CARRIERS 

IN 

INFECTIOUS  DISEASES 


A  MANUAL  ON  THE  IMPORTANCE,  PATHOLOGY.  DIAGNOSIS 
AND  TREATMENT  OF  HUMAN  CARRIERS 


HENRY  J.  NICHOLS,  M.D.,  M.A. 

Major,  Medical  Corps,  U.  S.  Army;  Instructor  in  Bacteriology, 

Parasitology  and  Preventive  Medicine,  Army  Medical 

School,  Washington,  D.  C. 


A  SECTION  ON 

CARRIERS  IN  VETERINARY  MEDICINE 

BY 

R.  A.  KELSER,  D.V.M.,  M.A. 

Captain,  Veterinary  Corps,  U.  S.  Army; 

In  Charge,  Veterinary  Laboratory,  Army  Medical  School, 

Washington,  D.  C. 


BALTIMORE 

WILLIAMS  &  WILKINS  COMPANY 

1922 


Copyright  1922 
WILLIAMS  &  WILKINS  COMPANY 

Made  in  United  States  of  America 

All  rights  reserved,  including  that  of  translation  into  foreign  languages, 
including  the  Scandinavian 


COMPOSED  AND  PMNTED  AT  THB 

WAVERLY  PRESS 

Bt  the  Williams  &  Wilkins  Compakt 

Baltimore,  Md.,  U.  8.  A. 


To 
The  Spirit  of  Science 

and 
The  Instinct  of  Service 


497775 


PREFACE 

In  writing  this  book,  the  author  has  attempted  to  prepare  a 
manual  on  that  young  but  rapidly  growing  specialty  in  preventive 
medicine,  which,  for  want  of  a  better  term,  may  be  called  carrier 
work.  The  subject  has  been  treated  as  a  part  of  general  medicine 
and  surgerj',  and  the  book  Ls  intended  to  be  of  practical  value  to 
medical  students  and  physicians,  especially  those  with  public 
health  responsibilities.  The  didactic  or  text  book  method  of 
presentation  haS;  therefore,  been  adopted,  rather  than  the  mono- 
graphic. There  are  already  two  monographs  on  this  subject  in 
English:  "The  Carrier  Problem  in  the  Infectious  Diseases,"  by 
Ledingham  and  Arkwright,  and  "Human  Infection  Carriers,"  by 
Simon.  The  writer's  aim  is  not  to  compete  with  these  valuable 
works,  but  to  supplement  them.  No  effort  is  made  to  develop 
the  subject  historically  or  bibliographically,  except  to  emphasize 
certain  points  or  to  refer  to  recent  sunmiaries.  The  idea  has  been 
to  give  a  systematic  exposition  of  current  medical  theory  and 
practice  as  relates  to  carriers.  Some  idea  of  the  amoimt  of  work, 
which  has  been  and  is  being  devoted  to  this  subject,  can  be  gath- 
ered from  the  fact  that  there  are  in  the  catalogue  of  the  Surgeon- 
General's  Library,  on  typhoid  carriers  alone,  over  three  hundred 
references  to  recorded  experiences.  An  effort  has  been  made  to 
collect,  from  these  sources  and  from  practical  experience,  the 
lessons  that  survive  the  test  of  time  and  trial  and  thus  deserve  a 
place  in  the  program  for  the  future. 

The  writer  has  had  personal  experience  with  carrier  problems 
from  several  different  angles.  On  the  theoretical  side,  anyone  who 
in  these  days  works  intelligently  for  the  health  of  groups,  as  well 
as  of  indi\'iduaLs,  soon  realizes  that  carriers  as  well  as  cases  must 
be  considered  in  any  rational  and  radical  program  for  the  control 
of  the  infec-tious  diseases.  In  attempting  to  study  carriers,  it  was 
found  that  animal  experimentation  afforded  a  good  method  of 
approach,  as  human  carriers  are  not  always  available  when  desired 
and  clinical  conditions  often  cannot  be  analyzed  experimentally. 

5 


PREFACE 

In  writing  this  book,  the  author  has  attempted  to  prepare  a 
manual  on  that  young  but  rapidly  growing  specialty  in  preventive 
medicine,  which,  for  want  of  a  better  term,  may  be  called  carrier 
work.  The  subject  has  been  treated  as  a  part  of  general  medicine 
and  surgerj^,  and  the  book  is  intended  to  be  of  practical  value  to 
medical  students  and  physicians,  especially  those  with  pubKc 
health  responsibilities.  The  didactic  or  text  book  method  of 
presentation  haS;  therefore,  been  adopted,  rather  than  the  mono- 
graphic. There  are  already  two  monographs  on  this  subject  in 
Enghsh:  "The  Carrier  Problem  in  the  Infectious  Diseases,"  by 
Ledingham  and  Arkwright,  and  "Human  Infection  Carriers,"  by 
Simon.  The  writer's  aim  is  not  to  compete  with  these  valuable 
works,  but  to  supplement  them.  No  effort  is  made  to  develop 
the  subject  historically  or  bibliographically,  except  to  emphasize 
certain  points  or  to  refer  to  recent  summaries.  The  idea  has  been 
to  give  a  systematic  exposition  of  current  medical  theory  and 
practice  as  relates  to  carriers.  Some  idea  of  the  amount  of  work, 
which  has  been  and  is  being  devoted  to  this  subject,  can  be  gath- 
ered from  the  fact  that  there  are  in  the  catalogue  of  the  Surgeon- 
General's  Library,  on  typhoid  carriers  alone,  over  three  hundred 
references  to  recorded  experiences.  An  effort  has  been  made  to 
collect,  from  these  sources  and  from  practical  experience,  the 
lessons  that  survive  the  test  of  time  and  trial  and  thus  deserve  a 
place  in  the  program  for  the  future. 

The  writer  has  had  personal  experience  with  carrier  problems 
from  several  different  angles.  On  the  theoretical  side,  anyone  who 
in  these  days  works  intelligently  for  the  health  of  groups,  as  well 
as  of  individuals,  soon  reahzes  that  carriers  as  well  as  cases  must 
be  considered  in  any  rational  and  radical  program  for  the  control 
of  the  infectious  diseases.  In  attempting  to  study  carriers,  it  was 
found  that  animal  experimentation  afforded  a  good  method  of 
approach,  as  human  carriers  are  not  always  available  when  desired 
and  clinical  conditions  often  cannot  be  analyzed  experimentally. 


6  PREFACE 

Some  personal  experimental  work  was,  therefore,  done  on  the 
mechanism  of  carrier  production,  and  on  the  possible  use  of 
animals  in  solving  carrier  problems.  On  the  practical  side,  it 
has  fallen  to  the  author's  lot  to  investigate  the  origin  of  several 
epidemics  in  which  the  carrier  possibility  was  a  proved  or  unproved 
factor.  Considerable  laboratory  work  in  the  bacteriological 
diagnosis  of  carriers,  the  virulence  of  cultures,  etc.,  has  also  been 
done  in  the  course  of  routine  duties.  Clinically,  before  and 
especially  during  the  war,  I  had  an  opportunity  to  test  the  results 
of  surgical  treatment  of  typhoid,  diphtheria  and  streptococcus 
carriers  and  am  convinced  of  the  value  of  these  measures.  During 
the  war,  survey  and  carrier  work,  which  was  done  on  a  larger  scale 
than  ever  before,  yielded  much  new  information.  Many  ques- 
tions of  policy  and  feasibiUty  were  also  raised.  Some  personal 
experience  with  such  problems  has  been  valuable  in  orienting  the 
subject.  Several  years'  experience  in  teaching  infectious  diseases 
at  the  Army  Medical  School  has  also  emphasized  the  importance 
of  the  subject  of  carriers  in  a  general  course.  Altogether,  there- 
fore, from  personal  experience,  the  author  believes  that  there  is 
a  place  for  a  practical  manual  on  carriers.  The  shortcomings  of 
this  attempt  are  realized,  but  it  is  hoped  that  these  pages  may 
assist  in  a  more  systematic  understanding  of  the  problem  and  may 
lead  to  more  effective  use  of  our  knowledge. 

It  is  a  pleasure  as  well  as  an  obhgation  to  acknowledge  much 
indebtedness  to  the  staff  and  organization  of  the  Laboratories  of 
the  Army  Medical  School,  under  the  Directorship  of  Lieutenant- 
Colonel  Charles  F.  Craig,  and  to  the  Curator  of  the  Army  Medical 
Museum,  Major  G.  R.  Callender,  of  the  Medical  Corps  of  the 
Army. 

Carriers  exist  in  the  infectious  diseases  of  animals  and  plants  as 
well  as  of  man,  and  the  comparative  or  biological  method  is  as 
valuable  in  the  study  of  carriers  as  it  is  in  other  branches  of 
medicine.  In  addition,  there  are,  of  course,  practical  carrier 
problems  for  veterinarians  and  horticulturists.  Plants  differ  in 
so  many  respects  from  man  and  animals  and  so  Httle  is  known 
about  their  mechanism  of  immunity,  that  this  field  can  not  be 
discussed  here  with  much  advantage.  Carriers  among  animals, 
however,  are  better  understood  and  are  analagous  to  human 


carriers.  In  fact,  all  our  animal  experimentation  is  a  part  of 
veterinary  medicine.  Moreover,  in  several  of  the  infectious  dis- 
eases, animal  carriers  directly  concern  physicians.  In  order  to 
cover  this  interrelated  field,  Captain  R.  A.  Kelser,  of  the  Veteri- 
nary Laboratory  of  the  Army  Medical  School,  has  contributed  a 
section  on  carriers  in  veterinary  medicine. 

This  publication  is  made  with  the  permission  of  the  Surgeon- 
General,  United  States  Army,  who,  however,  is  not  responsible  for 
any  opinion  expressed  or  conclusions  reached  herein. 


CONTENTS 

Introduction.     Definitions 13 

PART  I.    GENERAL  CONSIDERATIONS 

I.  Importance 21 

II.  Pathology 25 

III.  Diagnosis 34 

IV.  Treatment 37 

PART  II.    SPECIAL  DISEASES 

V.  The  typhoid  fevers 45 

VI.  Cholera 60 

Vll.  The  dysenteries 64 

a.  Bacillary 64 

b.  Protozoal 66 

VIII.  Helminthoses 70 

IX.  Diphtheria 72 

X.  Epidemic  meningitis 79 

XI.  Pneumococcus  pneumonia 87 

XII.  Streptococcus  infections 90 

Xni.  Other  respiratory  infections 97 

1.  Influenza 97 

2.  Vincent's  angina 98 

3.  Tuberculosis 99 

4.  Diseases  of  unknown  etiology  or  due  to  filterable  viruses.  100 
XIV.  Blood  diseases 101 

1.  Malaria 101 

2.  Other  diseases  of  the  blood 102 

3.  Skin   diseases 103 

XV.  Sexual  diseases 104 

1.  Syphilis 104 

2.  Gonorrhoea 106 

PART  III.    SmiMARY 

XVI.  The  relations  of  phorology  to  preventive  medicine Ill 

1.  The  place  of  carrier  work  in  preventive  medicine Ill 

2.  The  method  of  carrier  work 114 

3.  Carrier  work  in  the  military  services 116 


10  CONTENTS 

PART  IV.    CARRIERS  IN  VETERINARY  MEDICINE 
XVII.   Carriers  of  organisms  pathogenic  for  both  man  and  the  lower 

animals 123 

A.  Carriers  of  bacteria 123 

1.  Micrococcus  melitensis 123 

2.  Bacillus  tuberculosis 125 

3.  Organism  of  the  Salmonella,  Enteriditis  or  Gaertner 

group 129 

4.  Bacillus  tetani 132 

5.  Bacillus  oedematis  maligni 134 

6.  Bacillus  anthracis 135 

7.  Bacillus  mallei 136 

8.  Bacillus  diphtheriae 137 

9.  Bacillus  pestis 139 

10.  Bacterium  tularense 140 

11.  Bacillus  erysipelatis  suis 141 

12.  Miscellaneous  facultative-pathogenic  bacteria 143 

B.  Carriers  of  protozoa 145 

1.  Leishmania  canis 145 

C.  Carriers  of  filterable  viruses 147 

1.  Virus  of  foot-and-mouth  disease 147 

XVIII.  Carriers  of  organisms  pathogenic  for  animals  and  possibly  for 

man 151 

A.  Carriers  of  bacteria 151 

1.  Streptococcus  of  infectious  mastitis  of  cattle 151 

2.  Bacterium  abortus  (Bang) 153 

B.  Carriers  of  protozoa 156 

1.  Trypanosomes 156 

2.  Other  protozoal  and  metazoal  infections 159 

XIX.  Carriers  of  organisms  pathogenic  for  lower  animals  only 161 

A.  Carriers  of  bacteria 161 

1.  Bacillus  bipolaris  septicus 161 

2.  Bacillus  necrophorus 162 

3.  Bacillus  paratuberculosis 164 

4.  Bacillus  pullorum 166 

B.  Carriers  of  protozoa 167 

1.  Piroplasma  bigeminum  and  Piroplasma  bovis 167 

2.  Piroplasma  caballi  and  Nuttallia  equi 170 

C.  Carriers  of  filterable  viruses 171 

1.  The  virus  of  equine  infectious  anemia 171 

2.  The  virus  of  contagious  pleuro-pneumonia  of  cattle  . .  173 

3.  The  virus  of  equine  influenza 175 

4.  The  virus  of  hog  cholera 176 

XX.  Conclusion 177 

Index 181 


CONTENTS  11 

ILLUSTRATIONS 

1.  Section  of  tonsil  from  diphtheria  carrier 27 

2.  Section  of  tonsil  showing  yeast-like  parasite 28 

3.  Section  of  tonsil  with  crypts  injected  with  lampblack  and  paraffin.  29 

4.  Section  of  gall  bladder  of  typhoid  carrier 31 

5.  Section  of  gall  bladder  in  experimental  typhoid  carrier  in  rabbit.  32 

6.  Picture  of  duodenal  tube 52 

7.  Gall  bladder  from  typhoid  carrier  who  was   cured   by    cholecys- 

tectomy   56 

8.  Gall  bladder  from  typhoid  carrier  who  was  not  cured  by  cholecys- 

tectomy   57 

9.  Kidney  from  typhoid  carrier  who  was  cured  by  nephrectomy 58 

10.  Section  of  tonsil  of  diphtheria  carrier 75 

11.  Section  of  tonsil  of  streptococcus  carrier 93 


INTRODUCTION 

It  is  common  knowledge  that  the  recognition  of  the  infectious 
nature  of  many  diseases  made  a  new  era,  both  in  the  theory  and 
in  the  practise  of  medicine.  On  the  philosophical  side,  the  para- 
sitology of  Pasteur  and  Koch  soon  became  hnked  up  with  Darwin's 
grand  conceptions  and  has  taken  its  place  in  the  scheme  of  the 
struggle  for  existence  and  natural  selection.  On  the  practical  side, 
the  "germ  theory"  has  revolutionized  medicine  by  giving  us  much 
new  insight  into  and  control  over  many  diseases. 

Within  the  reahn  of  the  infectious  diseases,  the  concept  of  the 
so-called  healthy  carrier  was  also  epoch  making.  It  pointed  to 
a  new  possibihty  in  the  outcome  of  the  fight  of  man  against  his 
parasites.  The  patient  may  recover  with  complete  destruction  of 
the  parasite.  The  parasite  may  win  with  death  or  disabiUty  of 
the  patient.  But  there  may  also  be  a  draw  with  the  production 
of  a  carrier.  The  appreciation  of  this  possibility  lead  to  fresh 
progress  in  the  explanation  and  prevention  of  infections.  The 
original  observations  are  accredited  to  Koch  in  his  work  on  cholera 
in  1892-1893.  Work  on  typhoid  fever  developed  the  subject  and 
by  degrees  carriers  have  been  given  a  regular  place  in  the  picture 
of  infectious  diseases.  Most  of  our  exact  knowledge  has  come 
from  work  on  typhoid  and  diphtheria  carriers. 

It  may  be  accepted  that  the  continued  existence  of  many  infec- 
tious diseases  depends,  to  a  considerable  degree,  on  the  spread  of 
pathogenic  parasites  from  apparently  healthy  and  usually  immune 
individuals  to  susceptibles.  The  strength  of  the  carrier  program 
rests  on  the  possibility  of  detecting  such  parasites  and  such  sus- 
ceptibles and  of  keeping  them  separated.  This  possibility,  how- 
ever, depends  on  scientific  knowledge  and  on  administrative  con- 
trol, neither  of  which  is  complete.  In  many  diseases  we  have  no 
ready  means  of  determining  the  virulence  of  the  parasite  in  the 
possible  carrier  or  the  susceptibihty  of  the  possible  host.  In 
addition,  when  we  have  this  knowledge,  it  is  often  impossible  to 
apply  it  practically  on  a  large  scale  on  account  of  the  limitation  of 

13 


14  INTRODUCTION 

laboratory  facilities  and  because  the  affairs  of  life  are  not  run 
purely  for  preventive  medicine.  The  carrier  program,  therefore, 
admittedly  has  its  weak  points.  However,  with  the  increase  of 
the  exactness  of  our  knowledge  and  with  the  generalization  of 
scientific  education,  social  consciousness  is  calling  for  more  and 
more  carrier  work.  The  specialist  and  the  man  on  the  street  are 
gradually  joining  their  forces  for  a  strong  combined  attack  on  the 
carrier  problem. 

The  greatest  need  in  carrier  work  at  present  is  the  intelligent 
cooperation  of  medical  men  in  making  a  workable  synthesis.  Too 
often  the  bacteriologist  knows  only  his  germs,  the  physician  knows 
only  his  patient,  and  the  sanitarian  knows  only  the  gross  situation 
in  the  field.  Each  tries  to  construct  the  whole  story  from  his  own 
point  of  view  and  as  a  result  the  literature  contains  many  asser- 
tions, half  truths  and  guesses  which  hinder  real  progress.  The 
only  way  to  improve  is  for  all  concerned  to  get  closer  to  the  reali- 
ties and  to  cooperate  with  mutual  self-restraint. 

In  view  of  the  increasing  importance  of  the  subject,  a  special 
terminology  is  desirable.  The  term  "bacteriophoria"  has  been 
proposed  to  indicate  the  condition  of  carrying  bacteria.  But  this 
term  does  not  include  the  carrying  of  protozoa  and  metozoa  and 
does  not  cover  the  science  and  art  of  the  subject.  A  more  precise 
word  would  be  parasitophorology,  or  for  short,  phorology.  A 
carrier  would  be  a  phore,  or  a  phorist,  and  a  worker  on  carriers 
would  be  a  phorologist.  While  these  words  might  lend  them- 
selves to  ridiculous  developments,  such  as  treponemaphorologist, 
it  appears  that  phorology  and  phorologist  (medically  speaking) 
might  be  useful  at  times  and  they  are  suggested  for  consideration. 

A  carrier  is  an  individual  who  harbors  and  transmits  pathogenic 
parasites  without  showing  the  usual  evidences  of  infection.  Some 
carriers  show  no  cHnical  or  pathological  evidences  at  all  and  are 
really  healthy,  but  the  most  important  carriers  are  only  apparently 
healthy,  because,  on  careful  examination,  they  do  show  signs  or 
symptoms  of  local  infection.  Although  in  some  instances  the 
parasites  are  carried  purely  mechanically,  in  the  worst  carriers 
they  have  a  home  which  is  usually  a  slight  chronic  inflammatory 
lesion  of  a  mucous  membrane.  The  absence  of  disease  in  carriers 
is  due  to  the  fact  that  the  carrier  either  (1)  is  in  the  stage  of  incu- 


INTRODUCTION  15 

bation;  (2)  has  a  general  but  not  a  local  immunity;  or  (3)  is  too 
slightly  infected  to  show  symptoms. 
Carriers  may  be  classified  as  follows: 

1.  True  carriers 

A.  Incuhationary  carriers — temporary 

B.  Convalescent  carriers — temporary,   chronic  and 
relapsing 

C.  Contact  carriers — temporary  and   chronic,   pri- 
mary and  secondary. 

2.  Pseudo-carriers 

3.  Possible  carriers 

1.  True  carriers.  The  parasites  are  pathogenic  and  virulent. 
Questions  of  relative  virulence  are  of  course  involved  and  many  of 
them  are  unsettled  at  present.  The  weight  of  evidence,  however, 
is  against  sudden  changes  of  virulence  and  in  true  carriers,  accord- 
ing to  actual  tests  or  reasonable  assumption,  the  organisms  are  of 
sufficient  virulence  to  infect. 

A.  Incuhationary  or  precocious  carriers  are  infected  and  infec- 
tive individuals  in  the  incubation  period  of  various  diseases. 
These  carriers  are  recognised  as  especially  dangerous  in  the  acute 
exanthemata.  They  have  also  been  recognized  in  cerebrospinal 
meningitis,  typhoid,  cholera,  and  other  diseases.  In  some  car- 
riers the  germ  apparently  has  a  "resting"  period  much  longer  than 
the  chnical  incubation  period.  Even  with  the  ordinary  period  of 
days  and  weeks,  an  apparently  healthy  person  may  in  this  way 
spread  trouble  in  many  directions. 

B.  Convalescent  carriers  are  of  three  kinds,  the  temporary, 
chronic  and  relapsing. 

1.  Every  case  must  pass  through  the  temporary  convalescent 
carrier  stage  and  fortunately  most  cases  terminate  in  this  way. 
There  is  a  clean-up  fight  between  the  body  cells  and  the  parasite 
with  complete  victory  for  the  tissues.  Along  with  convalescence 
or  soon  afterwards,  the  patient  is  disinfected  by  immune  bodies 
and  phagocytes  and  does  not  infect  his  environment  or  immediate 
contacts. 

2.  A  small  percentage  of  convalescents,  however,  become 
chronic  carriers.  These  form  the  bulk  of  the  carrier  menace  and 
problem.    The  microorganisms  perpetuate  themselves  from  car- 


16  INTRODUCTION 

rier  to  case  and  from  case  to  carrier.  This  is  the  vicious  circle 
which  must  be  broken  to  win  the  fight  against  infectious  diseases. 

3.  Relapsing  carriers.  A  group  of  this  kind  is  useful  as  it  covers 
convalescent  carriers  who  later  relapse  into  cases.  Examples  of 
such  carriers  are  found  especially  in  protozoal  infections  in  which 
the  immunity  is  not  as  sharp  as  in  bacterial  infections.  The 
point  of  difference  between  a  chronic  or  latent  case  and  a  relapsing 
carrier  is  the  slowly  progressive  nature  of  the  infection  in  cases  and 
a  complete  balance,  even  if  temporary  in  carriers.  If  the  carrier 
conception  is  broadened  to  include  the  infection  of  one  organ 
within  the  individual  by  a  carrier  lesion  in  another  organ,  cases 
of  focal  infection  can  be  considered  relapsing  carriers. 

C.  Contact  carriers  or  "healthy"  carriers  are  those  who  acquire 
the  parasite  from  association  with  cases  or  carriers  without 
developing  the  disease  themselves.  Such  carriers  are  already 
immune.  Differential  diagnosis  between  a  contact  and  incuba- 
tionary  carrier  can  be  made  in  most  cases  only  by  the  outcome. 
Contact  carriers  are  usually  temporary,  but  may  become  chronic 
if  there  already  exists  some  predisposing  chronic  focus.  Thus, 
an  immune  contact  carrier  with  a  negative  Schick  test  and  an 
obstructed  nasal  passage  may  carry  diphtheria  bacilU  until  the 
deformity  is  corrected.  Contact  carriers  may  be  primary,  that  is, 
infected  by  a  case,  or  secondary,  infected  by  another  carrier.  The 
importance  of  pure  contact  carriers  has  been  exaggerated.  Many 
so-called  contact  carriers  are  really  convalescent  carriers  after 
mild  infections,  as  has  recently  been  emphasized  by  Craig. 

Contact  carriers  might  include  also  "mechanical"  carriers  such 
as  surgeons  with  contaminated  hands,  but  such  carriers  as  well 
as  inanimate  objects  which  carry  infection  by  indirect  contact 
are  best  considered  under  personal  hygiene  and  general  sanitation. 
There  is  nothing  distinctive  about  their  carrier  relationships. 

2.  Pseudo-carriers.  A  group  should  be  made  for  carriers  of 
non-pathogenic  and  non-virulent  organisms.  These  may  be  called 
pseudo-carriers.  In  any  extensive  carrier  work  suspicious  organ- 
isms are  found  which,  however,  on  further  examination,  turn  out 
to  be  of  no  importance.  In  the  meantime,  the  patient  may  have 
been  handled  as  a  true  carrier.  The  diagnosis  should  be  changed 
to  that  of  pseudo-carrier.  Such  carriers  are  especially  well 
recognized  in  diphtheria. 


INTRODUCTION  17 

3.  Possible  carriers.  A  group  of  possible  carriers  may  well  be 
made  to  account  for  the  considerable  number  of  persons  who  carry- 
organisms  of  uncertain  significance.  These  organisms  at  present 
can  neither  be  proved  nor  disproved  to  be  of  importance,  on  ac- 
count of  the  inadequate  state  of  our  knowledge.  Under  this  head- 
ing would  come  many  carriers  of  streptococci,  influenza  bacilli, 
and  various  intestinal  organisms.  With  increasing  knowledge 
this  group  will  naturally  disappear  as  the  members  of  it  are  dis- 
tributed among  the  true  and  psuedo-carriers. 

Convalescent  carriers  have  been  called  active  and  contact 
carriers,  passive.  These  terms  are  valuable  in  emphasizing  the 
difference  between  the  active  focus  of  multiplication  in  convales- 
cent carriers  and  the  usual  absence  of  a  home  in  the  contact 
carrier,  but  they  are  somewhat  misleading  as  all  true  carriers  are 
active  from  the  point  of  view  of  the  parasite. 

Cases  have  also  been  called  acute  carriers,  but  this  is  believed  to 
be  an  unfortunate  use  of  terms,  as  it  is  desirable,  on  many  grounds, 
to  distinguish  as  clearly  as  possible  between  cases  and  carriers. 

Insects  which  transfer  pathogenic  microorganisms  are  often 
called  carriers.  In  malaria,  the  mosquito  is  as  an  essential  part 
of  the  carrier  mechanism  as  the  formation  of  gametes  in  the 
blood.  The  final  result  is  also  the  same,  whether  typhoid,  dysen- 
tery or  cholera  germs  are  spread  by  the  fingers  of  a  carrier  or  by 
the  feet  of  a  fly.  But  the  subject  of  insect  carriers,  while  closely 
related  to  that  of  human  carriers,  practically,  deserves  separate 
consideration  theoretically. 

From  the  biological  point  of  view,  as  has  already  been  pointed ' 
out,  the  chronic  carrier  state  must  be  considered  as  the  result  of  a 
drawn  battle  between  mankind  and  its  parasites.  It  is  personal 
victory  as  the  invader  is  restricted  to  an  insignificant  position; 
it  is  a  social  defeat,  however,  as  the  invader  still  main- 
tains a  foothold  and  is  able  to  attack  new  individuals.  In  other 
words,  chronic  carriers  are  examples  of  the  balance  which  nature 
tends  to  establish  in  the  struggle  for  existence.  The  same  carrier 
balance  is  seen  in  the  whole  scale  of  life  from  the  lowest  to  the 
highest  forms.  Whether  in  plants,  animals  or  man,  parasites  are 
competing  with  hosts  in  the  infectious  diseases  and  the  carrier 
state  is  one  end  result.    Neither  side  wins  a  complete  victory. 


18  INTRODUCTION 

The  situation  is  compromised  and  infection  and  immunity  are 
balanced  against  each  other.  While  we  accredit  nature  with 
marvellous  adaptations  for  the  welfare  of  mankind,  it  should  not 
be  forgotten  that  a  typhoid  gall  bladder  or  a  diphtheria  tonsil 
represent  a  diabolical  mechanism  for  the  perpetuation  of  some 
of  man's  real  enemies.  It  is  the  aim  of  preventive  medicine  to 
break  up  this  balance  in  favour  of  man. 

Work  on  carriers  is  another  evidence  of,  and  argument  for,  the 
socialization  of  medicine.  The  extreme  individualism  of  the 
past  is  very  satisfactory  to  the  favored  few,  but  it  does  not  take 
into  consideration  the  welfare  of  the  many  who  make  up  the 
strength  of  the  nation  and  who  have  a  way  of  getting  what  they 
want  and  need.  The  care  of  the  individual  case  is  a  unit  of 
medical  attention,  but  it  is  only  part  of  an  adequate  program  for 
the  control  of  infectious  diseases.  The  carrier  is  also  a  problem 
which  requires  special  handling,  technical  and  administrative. 
In  addition  to  diagnosing  and  treating  the  case,  physicians  should 
learn  to  diagnose  and  treat  the  carrier  and  keep  pace  with  the 
increasing  social  demands  for  the  application  of  practical  measures. 
As  physicians  and  citizens  we  need  to  realize,  once  for  all,  that 
while  in  some  respects  the  individual  is  an  ultimate  unit,  in  others, 
he  is  only  a  part  of  higher  units,  the  family,  the  community,  and 
the  nation,  and  he  cannot  exist  without  them.  Hence,  medically 
as  well  as  biologically,  the  interests  of  the  whole,  that  is,  of  the 
race,  are  greater  than  those  of  the  individual  parts.  On  the  other 
hand,  it  is  the  individual  who,  in  the  long  run,  profits  from  the 
welfare  of  the  group. 

M.  G.  D.:  Brit.  Med.  Jour.,  1917,  ii,  633. 

Sacquepee,  E.  :  Les  Porteurs  de  germes.  Bulletin  de  L'Institut  Pasteur, 
1910,  8,  1,  321,  689. 

Ledingham  and  Arkwright:  The  Carrier  Problem  in  the  Infectious 
Diseases.     1912,  Edward  Arnold,  London. 

Simon,  C.  E.:  Human  Infection  Carriers.  1919,  Lea  and  Febiger,  Phila- 
delphia and  New  York. 

Craig,  C.  F.  :  Jour.  Amer.  Med.  Assoc,  1921,  Ixxvii,  827. 


PART  I 
GENERAL  CONSIDERATIONS 


CHAPTER  I 
Importance 

The  importance  of  carriers  is  two  fold.  In  the  first  place, 
chronic  carriers  constitute  more  or  less  permanent  reservoirs  of 
pathogenic  microorganisms.  Cases  are  usually  acute  and  the 
danger  of  spread  of  infection  is  limited  to  days.  The  chronic 
carrier,  however,  is  able  to  infect  his  environment  or  contacts  for 
months  or  years.  While  the  acute  case  excretes  more  germs  and 
probably  causes  most  cases  after  an  epidemic  starts,  the  carrier 
is  able  to  start  the  epidemic  itself  by  storing  the  germs  until 
seasonal  or  other  conditions  are  favorable  for  an  outbreak.  Some 
workers  claim  that  in  this  way  a  carrier  will  always  be  found  as  a 
connecting  link  in  any  considerable  series  of  cases.  According  to 
Vaughan,  one  of  the  principal  contributions  of  bacteriology  to 
epidemiology  is  the  teaching  about  carriers. 

Soon  after  the  recognition  of  the  infectious  nature  of  many 
diseases,  it  was  thought  that  the  environment  of  cases  was  heavily 
contaminated  with  germs.  In  this  period  efforts  were  directed 
especially  at  the  disinfection  of  water,  milk,  clothing,  and  fomites. 
It  was  soon  learned,  however,  that  many  pathogenic  germs  live 
outside  the  hosts  only  a  short  time  and  that,  while  much  can  be 
done  by  sanitation,  the  contact  avenue  of  infection  remains  largely 
open.  Attention  was  then  focused  on  the  case  itself.  It  was 
taught  that  if  all  acute  cases  were  detected  early  and  isolated  the 
streams  of  disease  would  dry  up.  But  again  it  was  soon  found  that, 
while  much  can  be  done  along  these  lines,  there  is  stUl  a  good  sized 
flow  from  the  carrier  reservoir.  At  present,  therefore,  much  at- 
tention is  being  devoted  to  this  other  personal  source  of  infection. 

The  second  reason  why  carriers  are  important  in  preventive 
medicine  is,  of  course,  the  fact  that  they  are  apparently  and  prac- 
tically healthy.  The  case,  confined  to  bed  or  to  a  sick  room, 
limits  the  spread  of  parasites,  consciously  or  unconsciously.  The 
carrier,  however,  usually  unaware  of  his  condition,  moves  about 
freely,  infecting  his  environment  or  contacts  without  notice.     It 

21 


22  CARRIERS   IN   INFECTIOUS   DISEASES 

is  this  circumstance  which  has  made  the  subject  so  dramatic  to  the 
laity  and  so  serious  to  the  profession. 

The  importance  of  carriers  varies  in  different  diseases.  In  a 
few  instances,  such  as  typhoid,  enough  information  is  becoming 
available  to  actually  estimate  the  number  of  cases  due  to  carriers 
as  compared  with  those  due  to  other  cases.  In  other  diseases  the 
exact  relative  importance  of  carriers  is  not  so  well  known,  but  the 
carrier  has  a  definite  place  in  the  epidemiology  of  cholera,  dysen- 
tery, diphtheria,  cerebrospinal  meningitis  and  malaria.  The 
organisms  can  be  identified  and  traced.  In  some  diseases,  such 
as  smallpox  and  measles,  carriers  are  not  important,  according  to 
usual  statements.  This  position  is  based  on  epidemiological 
evidence  which  may  or  may  not  have  been  rightly  interpreted. 
Until  more  is  known  about  the  organisms  causing  many  diseases, 
no  adequate  statements  can  be  made  about  their  carrier  aspects. 

There  is  undoubtedly  a  tendency  at  times  to  overestimate  the 
importance  of  carriers.  Other  cases,  including  mild  ones,  should 
be  considered  as  a  cause  of  a  given  case  before  a  carrier  is  sus- 
pected. It  should  also  be  remembered  that  many  so-called  car- 
riers are  really  pseudo-carriers  who  are  simply  parasitized  by  non- 
virulent  organisms.  Those  organisms  may  resemble  pathogenes 
morphologically  and  a  presumptive  diagnosis  may  be  made.  But 
virulence  tests  nearly  always  show  that  some  suspected  organisms 
have  no  significance.  Hence,  while  recognizing  the  real  impor- 
tance of  the  true  carrier  as  a  reservoir  of  pathogenic  parasites  and 
as  an  unadvertized  danger,  the  practitioner  of  preventive  medicine 
must  recognize  the  relative  importance  of  carriers  in  different 
diseases  and  the  existence  of  the  pseudo-carrier. 

On  the  other  hand,  there  is  in  some  quarters  a  tendency  to 
belittle  the  carrier  program  as  ineffective.  This  tendency,  I 
believe,  is  a  mistaken  one.  It  is  based  simply  on  our  insufficient 
knowledge  or  inadequate  control.  We  should  not  give  up  the 
advantage  won  by  the  known  existence  of  carriers  of  pathogenic 
organisms  because  we  cannot  always  assign  them  a  definite  place 
in  the  unknown  whirl  of  atoms  or  control  their  activities.  It 
should  be  realized  that  only  rarely  has  the  carrier  plan  of  attack 
^  on  an  infectious  disease  been  given  a  thorough  trial.  A  certain 
amount  of  work  has  been  done,  but  it  is  usually  not  complete  and 


IMPORTANCE  23 

radical  because  of  the  limitation  of  facilities  and  control.  The 
plan  breaks  down  because  the  work  is  too  extensive.  This 
circumstance  has  lead  some  workers  to  minimize  the  program. 
It  is  impossible,  however,  to  sucessfuUy  attack  the  principles  of 
phorology.  The  only  question  is  how  far  the  details  should  be 
carried  out.  As  laboratory  facilities  become  more  numerous  and 
reliable,  and  as  scientific  control  of  events  becomes  more  estab- 
lished, the  proper  amount  of  attention  will  be  given  to  this  rational 
plan  of  attack  on  our  competitors  in  life. 

The  importance  of  carriers  can  be  realized  by  considering,  first, 
the  percentage  of  cases  which  become  convalescent  carriers,  then 
the  percentage  of  contacts  who  become  contact  carriers  and  then 
the  percentage  of  both  kinds  of  carriers  in  the  general  population. 
Best  of  all,  however,  is  the  actual  demonstration  of  the  spread  of 
organisms  by  a  carrier  in  a  specific  group  of  cases. 

The  study  of  carriers  is  valuable  to  the  medical  student  as  it 
shows  him  something  of  the  biological  background  of  disease 
which  has  been  so  useful  in  orienting  the  medical  sciences.  Car- 
riers form  a  link  in  the  natural  history  of  disease.  To  understand 
them  is  to  acquire  a  liberal  medical  education  and  to  control 
them  is  to  aid  in  defending  and  extending  civilization.  The 
different  phases  of  carrier  work  involve  anatomy,  physiology, 
bacteriology,  parasitology,  pathology,  immunology,  medicine,  sur- 
gery, sanitation,  hospitalization,  quarantine  and  follow  up  service. 

The  general  practitioner  needs  to  know  the  best  teaching  about 
carriers  as  he  is  in  the  most  strategic  position  to  break  up  the 
parasitic  balance  in  favor  of  man.  Too  often,  either  through 
ignorance  or  limited  view  of  responsibility,  this  opportunity  is 
lost.  Patients  are  carried  through  a  severe  infection  with  skiU, 
but  are  turned  loose,  without  release  cultures,  to  inflict  the  same 
disease  on  others.  By  insisting  on  release  examinations  in  any 
case  whose  cause  can  be  found  by  such  examinations,  the  practi- 
tioner can  have  the  satisfaction  of  practising  preventive  medicine 
at  the  most  critical  period.  If  the  examination  is  negative,  the 
case  can  be  completely  closed  and  the  patient  is  better  satisfied. 
If  the  examination  is  positive,  the  patient  may  be  a  temporary 
convalescent  carrier  and  may  clear  up  with  a  short  extension  of 
convalescence.     If  the  case  becomes  a  chronic  carrier,  he  can  in 


24  CARRIERS    IN   INFECTIOUS   DISEASES 

some  instances  be  cured  and  at  least  he  can  be  instructed  in 
personal  hygiene.  If  he  does  not  respond  to  social  obligations, 
restrictive  measures  must  be  applied.  In  diphtheria,  this  ground 
is  already  covered  by  regulations,  but  in  several  other  diseases  the 
practitioner  decides  what  shall  or  shall  not  be  done.  It  is  much 
easier  to  ignore  this  subject,  but  microorganisms  can  not  be 
trusted.  There  will  be  no  general  advance  in  the  prevention  of 
many  diseases  until  the  general  practitioner  helps  by  detecting 
and  handling  convalescent  carriers. 

Most  of  all  the  public  health  official  must  realize  the  importance 
of  carriers  as  his  position  is  due  to  a  social  demand  for  supervision 
of  the  health  of  groups,  among  whom  carriers  are  sure  to  be  found. 
He  must  officially  be  in  position  to  diagnose  and  handle  carriers. 
Carrier  work  among  private  physicians  is  largely  voluntary  and 
depends  on  the  degree  of  social  consciousness  of  the  individual. 
The  public  health  official,  however,  is  paid  to  be  socially  minded. 

The  organization  includes,  first,  the  laboratory  for  the  discovery 
of  carriers,  and  second,  regulations  to  secure  appropriate  action. 
The  needs  of  the  laboratory  are  more  fully  discussed  under  the 
heading  of  diagnosis.  It  is  sufficient  to  say  here  that  nowhere 
can  the  laboratory  facilities  be  considered  adequate  for  the  work 
that  might  be  done.  Of  course  the  question  is  an  economic  and 
social  one.  Do  the  results  justify  the  expense  and  trouble?  The 
answer  here  as  elsewhere  seems  to  be  that,  as  scientific  knowledge 
increases,  there  is  an  increasing  demand  for  its  application  in  the 
amelioration  of  human  life. 

On  the  administrative  side,  there  are  many  perplexing  questions 
of  policy  in  handling  carriers.  The  uncertainty  of  our  knowledge 
in  some  diseases  and  the  fallability  of  laboratory  workers  often 
add  to  the  confusion.  But  one  point  should  be  kept  clear.  The 
interests  of  the  group  of  race  are  supreme  over  those  of  the  in- 
dividual. This  decision  has  been  handed  down  by  Nature  and 
by  Society  and  other  decisions  must  conform.  The  interference 
with  the  individual  should  be  as  shght  as  possible,  but  there 
should  be  no  question  about  the  principle  that  governs. 

Vaughan,  V.  C:  Epidemiology  and  Public  Health.     1922,  C.  V.  Mosby 

&  Co.,  St.  Louis. 
CoNKLiN,   E.    G.:  The   Direction   of  Human  Evolution.     1921,    Charles 

Scribners  Sons,  New  York, 


CHAPTER  II 
Pathology 

The  pathology  of  carriers  inchides  specific  lesions  and  a  general 
or  local  immunity.  The  anatomical  basis  is  an  important  factor, 
but  immune  reactions  underlie  the  phenomenon  as  a  whole. 
While  there  are  many  unknown  elements  in  the  equilibrium  be- 
tween host  and  parasite  as  seen  in  carriers,  there  is  also  available 
much  actual  knowledge  or  suggestive  information. 

In  the  temporary  contact  carrier  there  is  probably  no  demonstra- 
ble lesion.  The  organisms  apparently  live  and  multiply  for  a 
short  time  on  mucous  surfaces  and  then  die  off  or  are  washed  away 
by  the  secretions.  The  tissues  are  immune  and  in  the  absence 
of  actual  proof  the  most  that  can  be  imagined  is  a  slight  preexist- 
ing lesion  which  produces  an  i^icreased  secretion  of  mucus  as  a 
temporary  focus. 

In  the  chronic  contact  carrier,  however,  some  definite  preexist- 
ing lesion  is  often  found  upon  which  the  parasite  becomes  in- 
grafted. There  is  probably  a  slight  re-infection  in  the  immune 
host.  As  soon  as  the  cause  of  the  primary  lesion  is  removed,  as, 
for  example,  by  extraction  of  a  foreign  body  or  the  correction  of  a 
deformity,  the  carrier  state  becomes  temporary  again.  The 
carrier  lesion,  in  itself,  is  here  again  very  superficial. 

The  lesion  of  the  incubationary  carrier  is  of  course  the  slight 
inflammation  produced  in  the  tissues  by  the  first  invasion  of  the 
parasite  and  its  early  multiplication.  Natural  lesions  of  this 
kind  are  rarely  obtained  for  study,  but  experimental  lesions  fill 
in  this  gap.  In  the  early  stages  of  infection,  the  microorganisms 
are  found  on  the  epithelial  surfaces,  penetrating  between  the  cells 
(Cecil  and  Blake) .  There  is  some  capillary  dilatation  and  oedema 
and  a  migration  of  leucocytes.  Once  past  the  epithelial  barrier 
the  organisms  spread  along  the  lymphatics,  multiply  and  break 
out  again  through  the  epithelial  covering  into  open  spaces.  The 
course  of  the  lesion  is  then  the  usual  one  for  the  specific  organism. 
From  the  carrier  point  of  view,  the  important  fact  is  that,  during 

25 


26  CARRIERS   IN   INFECTIOUS    DISEASES 

this  early  period,  there  is  often  the  greatest  multipHcation  of  the 
parasite  and  hence  the  greatest  danger  of  transmission. 

The  lesion  of  the  chronic  convalescent  and  relapsing  carrier  is  the 
most  definite  one.  It  is  also  the  most  persistent,  the  most  dan- 
gerous and  requires  the  most  treatment.  The  lesion  is  a  small 
surviving  infection  in  a  generally  immune  host.  It  dates  back  to 
the  original  attack  and  has  survived  the  processes  which  have  pro- 
tected the  individual  as  a  whole.  The  organisms  are  walled  off 
or  protected  from  the  immune  mechanisms  and  live  on  indefinitely 
■ — as  balance  is  reached.  The  lesion  may  be  slight,  even  micro- 
scopic, but  has  been  found  with  great  regularity  in  the  best  known 
carrier  conditions. 

There  are  two  especially  important  sites  of  chronic  convalescent 
inflammation — the  tonsil  and  the  gall  bladder.  Other  similar 
foci  occur  in  other  parts  of  the  body,  but  the  lesions  of  these  two 
organs  may  be  taken  as  types,  one  of  the  large  field  of  respiratory 
carriers  and  the  other  of  the  large  field  of  intestinal  carriers. 
Chronic  tonsillitis  and  cholecystitis  should,  therefore,  be  con- 
sidered in  some  detail. 

Chronic  tonsillitis.  This  lesion  explains  the  existence  of  many 
carriers  of  virulent  diphtheria  bacilli  and  hemolytic  streptococci. 
It  is  probably  also  primarily  or  secondarily  responsible  for  carriers 
of  pneumococci,  meningococci,  staphylococci,,  influenza  bacilli  and 
the  organisms  of  Vincent's  angina.  Filterable  viruses  are  also 
carried  in  the  tonsils. 

One  of  the  recognized  functions  of  the  tonsils,  adenoids 
and  other  lymphatic  structures  of  the  upper  respiratory  and 
alimentary  tract  is  to  help  protect  the  body  from  infection. 
Pathogenic  bacteria  are  picked  up  by  these  phagocytic  lymphoid 
structures  and  an  attempt  is  made  to  destroy  them,  as  in  acute 
tonsillitis.  This  function  is  undoubtedly  a  valuable  one  and  ac- 
cording to  the  general  consensus  of  opinion  should  be  preserved 
early  in  life.  In  many  cases,  however,  this  function  becomes 
perverted.  The  tonsil  is  unequal  to  its  task  and  the  microor- 
ganisms, instead  of  being  killed,  find  a  permanent  home.  The 
policeman,  instead  of  arresting  the  criminal,  is  forced  to  become 
an  accomplice.  Under  these  circumstances  the  tonsil  becomes 
an  individual  and  social  liability  rather  than   an   asset.     It  is 


PATHOLOGY 


27 


often  best  to  lose  the  perverted  protective  function  by  removal 
of  the  organ  or  by  X-ray  treatment. 

The  average  tonsil  is  not  normal  in  the  sense  of  healthy  lym- 
phoid   tissue    covered    with    intact    epithelium.     Almost    every 


Fig.   1.  Section   of  Toxsil   of   Chronic   Diphtheria  Carrier.     X  50 
Shows  loss  of  epithelium  and  fibrinous  exudate  in  tissue 

tonsil  which  is  examined  shows  some  disintegration  of  epithelial 
covering  with  exudation  and  signs  of  inflammation,  due  to  infec- 
tion with  various  pathogenic  parasites  (fig.  1).  In  addition  to 
these  and  as  illustrating  the  favorable  conditions  for  parasitism, 


28  CARRIERS   IN    INFECTIOUS    DISEASES 

various  other  harmless  parasites  are  found,  such  as  amoebae  and 
leptothrices.  An  undescribed  yeast-like  organisms  with  no  in- 
flammatory reaction  about  it  is  present  frequently  in  sections 
(fig.  2). 


Ik;.    2.  (xidkntified    Yeast-Like   Organisms   Frequently   Found    in  Sections  of. 

ToNsiLP.  X  400 
MacCallum  stain.     Note  absence  of  reaction  around  parasites 

The  tonsil,  therefore,  is  often  a  hot  bed  for  microorganisms. 
The  crypts  become  incubators  instead  of  disinfectors.  Heat, 
moisture  and  food  are  supplied  by  the  body  while  the  antiseptic 
action  of  the  tissues  and  body  fluids  is  neutralized  by  poor  drain- 
age.    The  structure  of  the  crypts  with  their  blind  ends,  tortuous 


PATHOLOGY  29 

channels  and  "underground"  connections  make  an  ideal  nest  or 
home  for  thes(>  parasites  (fig.  3).  With  such  an  organ  as  this  at 
the  gateway  to  the  body,  it  is  easily  realized  that  the  chances  for 
carrier  production  are  particularly  good.  Temporary  and  chronic 
convalescent  carriers  are  especially  apt  to  develop. 

The  same  situation  exists  with  less  frequency  in  lesions  of  the 
sinuses,  turbinates,  septum,  gums  and  other  structures  of  the  nose 
and  mouth. 


Fig.  3.  Photograph  of  Tonsil  Injected  with    Lampblack  and  Paraffin 

TO  Show  Crypts 

"Underground"  connecfions  are  emphasized.     Preparation  by  Sturm 

Chronic  cholecystitis.  The  gall  bladder  has  of  course  an  entirely 
different  function  from  the  tonsil,  but,  in  its  carrier  relationship,  the 
entire  gall  bladder  may  be  compared  to  a  crypt  of  the  tonsil.  The 
wall  is  slightly  invaded  in  a  chronic  process  and  the  contents  consist 
of  a  rich  culture  of  typhoid  or  cholera  bacilli.  Apparently  the 
bile  neutralizes  the  antiseptic  effect  of  the  leucocytes,  mucus  and 
serum,  while  the  addition  of  these  substances  increases  the  nutri- 


30  CARRIERS   IN    INFECTIOUS    DISEASES 

tious  value  of  the  bile.  The  result  is  a  very  effective  multiplying 
and  distributing  agency. 

Much  work  and  speculation  have  been  devoted  to  the  subject 
of  the  mechanism  of  gall  bladder  infection.  The  possibilities  of 
infection  are  (1)  ascending,  through  the  common  and  cystic  ducts 
from  the  intestine,  (2)  embolic,  in  the  blood  and  lymph  vessels  of 
the  bladder  wall,  (3)  descending,  through  the  bile  from  the  liver. 
Any  of  these  methods  may  occasionally  occur,  but  ascending  in- 
fection is  apparently  rare.  Evidence  from  some  expermiental 
work  in  rabbits  seems  to  favor  an  early  small  embolic  lesion  of 
the  wall  with  subsequent  general  infection  of  the  contents  and 
wall  (Meyer).  Other  experimental  work  favors  the  descending 
route,  as  large  numbers  of  bacteria  are  excreted  from  the  blood  by 
this  method  and  an  inspissation  of  bile  is  known  to  occur  in  the 
bladder.  This  theory  also  draws  some  support  from  the  fact  that 
a  large  number  of  carriers  occur  among  women  in  whom  biliary 
stasis  is  more  frequent.  The  important  fact  is  that,  whatever  the 
earliest  lesion,  the  end  result  is  a  general  mild  catarrhal  inflam- 
mation of  the  wall  with  infection  of  the  contents  of  the  cavity. 

The  cholecystitis  starts  as  an  acute  mild  process  during  the 
original  disease  and  persists  indefinitely.  When  examined  after 
operation  or  autopsy,  these  gall  bladders  have  a  thickened  wall 
and  altered  contents.  The  ordinary  uniform  brown  bile  is  re- 
placed by  a  yellowish  or  whitish  fluid  with  sediment  of  purulent 
flakes.     One  or  more  gall  stones  are  present. 

The  wall  shows  a  general  catarrhal  inflammation.  Ulceration 
does  not  occur  except  possibly  early  and  no  lesions  of  the  wall  are 
found  except  in  the  submucosa.  Here  there  is  a  uniform  collection 
of  Ijanphocytes  indicating  a  reaction  to  infected  contents  (fig.  4). 
The  epithelial  wall  may  show  nests  of  bacilli  (fig.  5) . 

The  carrier  state  can  be  produced  experiinentally  in  a  certain 
percentage  of  rabbits  by  intravenous  injection.  The  gall  bladder 
lesions  are  of  value  in  attempts  at  chemotherapy  and  for  demon- 
stration. Gay  and  Claypole  state  that  by  a  special  technique 
they  are  able  to  make  100  per  cent  of  carriers.  Ordinarily,  about 
30  per  cent  of  carriers  result  from  the  injection  of  sub  lethal  doses. 
Freshly  isolated  cultures  are  most  effective. 


PATHOLOGY  31 

In  some  carriers  the  surviving  lesion  seems  to  1)(>  confined  to  the 
gall  bladder  as  excision  of  this  organ  results  in  bacteriological  cur(\ 
In  others,  however,  there  must  be  other  lesions  in  other  parts  of 
the  biliary  system,  probably  higher  up  in  the  smaller  bile  capil- 


r<%' 


Fig.  4.  Section  op  Gall  Bladder  in  Human  Typhoid  Carrier.     X  70 
The  section  shows  that  the  lesion  is  confined  to  the  mucous  membrane 
of  the  bladder.     There   is  a  mild    general    catarrhal  inflammation  with 
migration  of  leukocytes  into  the  submucosa. 

laries,  because  cholecystectomy,  in  some  carriers,  does  not  result 
in  cure.  No  practical  way  of  determining  the  existence  of  exact 
location  of  this  lesion  is  available  at  present.  These  lesions  of  the 
liver  in  carriers  are  not  well  understood  but  they  may  originate 
in  the  so-called  focal  necroses  which  are  really  emboli  of  endothe- 


32 


CARRIERS   IN   INFECTIOUS   DISEASES 


lial  cells.  In  experimental  work,  infection  of  the  smaller  bile 
capillaries  occurs  with  the  production  of  multiple  cysts  resembling 
a  bunch  of  grapes. 


Ek,-.  ••iyi-.SiY.i 


/r> 


..##. 


■^ 


0» 


0 


Fig.  5.  Drawing  of  Section  of  Gall  Bladdp:r  ix  Experimental  Typhoid 
Carrier  State  in  Rabbit.     X  800 
Nest  of  typhoid  bacilli  is  seen  in  epithelial  coat   and  the  collection  of 
leukocytes  is  seen  in  the  submucous  coat. 


PATHOLOGY  33 

The  other  lesions  of  intestinal  carriers  are  chronic  ulcers  of  the 
intestines  which  will  be  discussed  under  dysentery. 

The  lesions  of  the  urinary  carrier  are  much  the  same  as  those  of 
the  intestinal  carrier.  The  lesion  is  really  in  the  hilum  of  the 
kidney' — a  chronic  pyelitis  with  secondary  cystitis.  The  lesion 
is  a  surviving  one  and  the  same  questions  of  pathogenesis  arise 
as  in  case  of  the  cholecystitis. 

In  addition  to  the  actual  lesion,  the  general  state  of  immunity 
of  the  body  is  of  great  importance  in  carriers.  In  incubationary 
carriers  there  is  naturally  no  immunity  or  only  a  beginning  one. 
In  convalescent  carriers  there  is  a  general  immunity,  but  not  a 
local  one.  In  some  instances  the  carrier  state  probably  keeps  up  an 
immunity  bj^  continuous  vaccination.  The  organisms  in  the 
focus  stimulate  the  formation  of  immune  bodies  such  as  agglu- 
tinins, opsonins,  bacteriolysins  and  complement  fixing  bodies. 
These  are  not  present  regularly  or  in  strong  concentration  and 
suggest  a  balanced  immunity.  In  relapsing  carriers  the  balance 
is  delicate  and  easily  upset,  especially  in  protozoal  infections.  In 
true  contact  carriers  there  is  a  general  or  local  immunity.  No 
evidence  is  found  of  active  immune  processes. 

Cecil,  A.  L.,  and  Blake,  F.  G.  :  Jour.  Exp.  Med.,  1920. 

Barnes,  H.  A. :  The  Tonsils,  Faucial,   Lingual  and  Pharyngeal.     1914, 

C.  V.  Mosby  Company,  St.  Louis. 
Meyer,  K.  F.:  Jour.  Inf.  Dis.,  1921,  xxviii,  381. 
Nichols,  H.  J.:  Jour.  Exp.  Med.,  1916,  xxiv,  497. 
Rous,  Peyton  and  McM aster,  P.  D. :  Jour.  Exp.  Med.,  1921,  xxxiv,  47. 
Bloomfield,  a.  L.  :  Bulletin  of  the  Johns  Hopkins  Hospital,  1921,  xxxii. 


CHAPTER  III 

Diagnosis 

The  adequate  diagnosis  of  a  carrier  involves  (1)  the  identifica- 
tion of  the  specific  parasite,  or  of  specific  immune  substances; 
(2)  the  location  and  significance  of  the  focus  in  the  host;  (3)  the 
relation  of  the  carrier  to  his  environment  and  contacts.  The 
diagnosis  is,  therefore,  a  combined  one  depending  on  laboratory, 
clinical  and  epidemiological  work  and  should  be  accomplished  by 
"cooperation"  rather  than  by  "competition"  between  the  pathol- 
ogist, the  physician  and  the  sanitarian.  Of  course,  some  one 
gifted  and  energetic  individual  may  in  turn  find  the  germ,  examine 
the  patient  and  follow  the  trail  in  the  group.  This  has  been  the 
most  common  method  in  the  development  of  the  carrier  work  and 
undoubtedly  it  is  best  for  some  one  person  to  gather  up  all  the 
threads  of  the  story.  As  the  whole  carrier  movement  started  in 
the  laboratory,  the  laboratory  specialist  often  takes  the  lead,  or 
is  expected  to  do  so.  But  the  work  has  now  reached  the  stage 
where  more  organization  is  needed.  No  one  person  can  do  justice 
to  all  aspects  of  the  situation.  The  requisite  for  effective  work  is 
the  intelligent  cooperation  of  all  concerned. 

In  the  laboratory  diagnosis,  the  finding  of  the  specific  organism 
is  usually  the  aim.  Details  of  suitable  methods  are  given  later 
under  each  infection.  In  general  it  may  be  said  that  specific 
diagnosis  is  more  difficult  in  carriers  than  in  cases.  There  are 
usually  more  individuals  to  be  examined.  The  organisms  are 
usually  less  numerous  and  may  be  more  mixed  with  other  organ- 
isms. In  addition,  there  is  more  doubt  about  virulence  and,  if 
virulence  tests  are  available,  these  must  be  made.  There  are  also 
increasing  complexities  of  groups  and  subgroups  which  must  be 
considered. 

In  some  diseases  a  tentative  diagnosis  can  be  made  on  the  pres- 
ence of  antibodies,  which  are  as  specific  as  the  parasite  itself. 
Of  the  antibodies,  the  agglutinins  are  the  easiest  to  detect  and 
have  been  most  used.     As  far  as  is  known,  they  are  as  reliable  as 

34 


DIAGNOSIS  35 

any  others  in  carrier  work.  Agglutination  is  an  especially  valuable 
measure  in  dealing  with  veterinary  carriers.  Allergic  skin  tests 
have  been  proposed  as  an  aid  in  detecting  carriers.  If  reUable, 
such  tests  would  be  of  great  value.  As  yet,  however,  they  are  not 
on  a  practical  basis  in  human  medicine.  Naturally  all  these 
immune  reactions  are  indications  only  of  infection.  They  do  not 
distinguish  between  a  case  and  a  carrier,  but  they  may  aid  in  the 
final  diagnosis. 

In  addition  to  attempting  to  find  the  parasite  or  evidences  of 
its  presence,  the  laboratory  may  be  called  on  to  determine  the 
susceptibility  of  possible  hosts  or  at  least  to  supply  the  biological 
materials,  if  such  tests  are  practicable. 

It  is  evident  that,  with  this  primary  dependence  on  laboratory 
methods,  the  work  of  the  laboratory  must  be  reliable.  The 
clinical  check  is  slight  at  best.  Hence,  the  personnel  and  equip- 
ment of  a  phorological  laboratory  must  be  even  better  than  those 
of  a  laboratory  of  clinical  pathology.  The  pure  technician  is, 
therefore,  of  lunited  value  in  carrier  work.  The  type  needed  is  the 
specialist  who  has  emerged  from  a  general  medical  background. 
As  has  abeady  been  said,  laboratory  facilities  have  practically 
never  been  sufficient  for  the  work  which  might  be  done.  If 
carrier  work  is  worth  while,  as  it  seems  to  be,  more  support, 
financial  and  moral,  should  be  given  to  the  laboratory. 

The  clinician  can  aid  in  the  finding  of  the  parasite  by  picking  out 
suspects  for  examination.  Meningococcus  carriers  are  more  apt 
to  be  found  among  persons  with  large  amounts  of  mucus  in  the 
nasopharynx  and  streptococcus  carriers  among  those  with  large 
tonsils.  Typhoid  carriers  sometimes  have  local  signs  or  symptoms 
of  cholecystitis.  The  personal  history  of  disease  is  also  often 
suggestive.  Another  useful  field  of  clinical  activity  exists  in  the 
actual  securing  of  a  satisfactory  specimen  for  laboratory  examina- 
tion. Much  lost  motion  and  confusion  results  from  the  examina- 
tion of  poor  specimens.  To  obtain  a  good  specimen  from  the 
tonsils,  nasopharynx,  sinuses,  duodenum,  or  ureters  requires  con- 
siderable technique  which  should  be  furnished  by  the  clinician  or 
by  his  organization  of  technical  assistants  and  nurses. 

After  the  presence  of  a  virulent  organism  in  the  body  has  been 
established,  a  clinical  survey  is  necessary  to  locate  the  focus,  to 


36  CARRIERS   IN   INFECTIOUS   DISEASES 

decide  the  diagnosis  between  a  carrier  and  a  mild  case  or  to 
classify  the  carrier.  This  work  can  be  properly  done  only  by  a 
clinician.  Altogether,  therefore,  the  physician  has  an  important 
part  to  play  in  the  diagnosis. 

Like  the  clinician,  the  epidemiologist  can  assist  in  the  diagnosis 
by  picking  out  the  most  suspicious  individual  or  group  for  ex- 
amination. Of  course  the  possible  contacts  and  sources  of  in- 
fection are  often  innumerable  and  the  most  effective  method 
would  be  a  complete  examination  of  all  persons.  There  would 
then  be  available  a  complete  record  of  their  parasitological  status. 
But  such  a  state  of  affairs  is  for  Utopia,  not  for  our  work-a-day 
world.  The  medical  Sherlock  Holmes  can  often  get  a  clue  from 
the  general  situation  which  can  be  followed  up  in  the  laboratory. 
The  number  to  be  examined  can  often  be  narrowed  so  that  a  few 
persons  can  receive  especial  attention.  This  result  requires,  of 
course,  the  usual  epidemiological  investigations  of  personal  habits, 
occupation,  journeys,  and  so  forth. 

When  the  carrier  is  once  diagnosed,  individually,  the  epidemi- 
ologist must  be  depended  on  to  make  the  social  diagnosis.  The 
finding  may  mean  much  or  little  according  to  circumstances. 
Hence,  in  the  last  analysis,  the  epidemiologist  should  be  the 
coordinator  in  carrier  work. 


CHAPTER  IV 

Treatment 

The  treatment  of  carriers  has  one  unusual  factor.  UnHke  the 
case,  the  carrier  must  be  convinced  that  he  needs  medical  atten- 
tion. The  correction  of  the  trouble  also  has  more  social  than 
individual  value.  Hence,  self-interest  is  often  directly  against 
any  treatment.  The  situation  should  be  handled  along  the  fol- 
lowing lines.  Carriers  usually  have  chronic  infections.  These 
maj^  become  acute  at  tunes  and  make  more  trouble.  Moreover, 
all  current  medical  teaching  favors  the  removal  of  chronic  foci 
of  infection  for  the  good  of  the  individual.  Hence,  a  carrier  has 
personal  reasons  for  being  treated.  In  addition,  the  interests  of 
society  are  paramount  to  those  of  the  individual.  The  individual 
should  recognize  his  social  obligations  and  as  far  as  possible  not 
do  harm  to  others.  If  he  is  unwilling  to  accept  this  point  of  view 
he  may  be  forced  to  it.  As  was  shown  in  the  great  war,  society 
will  not  tolerate  individual  action  which  is  anti-social  in  emer- 
gencies, and  cases  of  infectious  disease  are  more  and  more  being 
regarded  as  emergencies.  Reason  is  effective  with  many  carriers 
discipline  with,  others,  but  some  can  be  handled  only  bj^  force. 

The  treatment  of  carriers  includes  technical  methods,  instruc- 
tion in  personal  hygiene  and  administrative  or  legal  measures. 

The  technical  treatment  of  infections  as  applied  to  carriers 
consists  of  the  following  procedures: 

a.  Good  hygiene,  local  and  general,  to  assist  in  the  natural 
processes  of  combatting  microorganisms.  These  measures  are 
especially  valuable  in  handling  temporary  contact  carriers,  such 
as  meningococcus  carriers. 

b.  Specific  anti-microbic  treatment,  which  consists  of  the  use 
of  vaccines  and  sera.  These  measures  in  general  have  been  dis- 
appointing, but  analogy  and  partial  success  keep  alive  the  possi- 
bility that  these  measures  may  some  time  be  effective.  As  the 
focus  in  convalescent  carriers  has  persisted  in  spite  of  a  general 
immunity  which  has  practically  cured  the  patient,  little  effect 

37 


38  CARRIERS   IN   INFECTIOUS    DISEASES 

might  be  anticipated  from  specific  vaccines  or  sera.  In  fact, 
experience  has  shown  that  typhoid  vaccination  does  not  cure 
typhoid  carriers  with  any  regularity  and  diphtheria  antitoxin  and 
vaccine  do  not  cure  diphtheria  carriers.  The  whole  subject  of 
the  therapeutic  use  of  vaccines  is  in  such  a  state  of  uncertainity 
that  definite  statements  cannot  be  made. 

The  use  of  non-specific  vaccines  has  also  been  tried  with  the 
idea  of  producing  a  reaction  which  might  clean  up  a  carrier 
lesion  in  the  same  way  that  it  sometimes  affects  other  chronic  foci. 
This  measure  may  have  turned  the  balance  in  some  carriers,  but 
many  are  resistant. 

c.  The  local  use  of  disinfectants.  This  is  a  logical  procedure 
but  is  not  completely  successful  in  practise.  The  number  of 
organisms  may  be  reduced  and,  with  this  reduction,  the  danger  of 
transmission  may  be  lessened,  but  cure  is  not  regularly  attained. 
During  the  war,  elaborate  devises,  such  as  gassing  chambers,  were 
used  for  the  large  number  of  carriers.  The  consensus  of  opinion 
is  that  specific  action  was  not  proved.  In  some  instances,  the 
antiseptics  seemed  to  injure  the  natural  resistance  of  the  mucous 
membrane  and  the  organisms  grew  out  in  pure  culture. 

d.  Specific  chemotherapy.  The  carrier  has  been  a  particularly 
attractive  subject  for  workers  in  chemotherapy  and  a  great  many 
compounds  have  been  tried  experimentally,  especially  in  gall 
bladder  infections.  At  present  it  cannot  be  said  that  any  one 
compound  has  won  its  way  clinically  except  the  arsphenamine 
series  in  spirochete  carriers.  Mercury,  quinine,  emetine  and 
antimony  of  course  have  their  place  in  the  treatment  of  carrier 
infection. 

e.  The  most  successful  local  method  of  treating  carriers  is  the 
removal  of  the  focus  by  surgical  operation.  This  measure  has 
been  successful  in  over  50  per  c^nt  of  typhoid  carriers  and  in  over 
:80  per  cent  of  diphtheria  carriers.     Under  this  head  come  also 

corrective  measures,  such  as  the  removal  of  foreign  bodies  and  the 
opening  of  obstructed  air  passages.  X-ray  and  radium  have  been 
tried  as  a  substitute  for  surgery.  They  have  failed  to  influence 
gall  bladder  lesions,  but  in  some  instances  contract  the  tonsil 
and  may  be  a  method  of  choice  under  certain  circumstances. 
Unfortunately  the  lesion  may  be  reduced  but  the  organisms  may 


TREATMENT  39 

persist.     Repeated  treatments  may  be  necessary  and,  for  prompt 
and  permanent  results,  tonsillectomy  is  preferable. 

The  results  of  surgical  treatment  of  carriers  confirm  the  conclu- 
sion drawn  from  experimental  and  pathological  study  of  the  sub- 
ject, namely,  that  the  chronic  carrier  state  is  really  an  infection  ' 
which  is  usually  sharply  localized. 

The  surgical  treatment  of  carriers  calls  for  cooperation  on  part 
of  the  surgeon.  The  diagnosis  is  usually  made  by  physicians  and 
the  surgeon  is  asked  to  give  technical  assistance  only.  At  the 
same  time,  he  should  accept  the  program.  Some  surgeons  decline 
to  operate  except  on  cases,  but  this  is  a  limited  view  of  the  possi- 
bilities and  responsibiUties  of  surgery. 

Aside  from  purely  technical  treatment  there  is  with  carriers  an 
especial  reason  for  "treating  the  patient  as  well  as  the  disease." 
The  carrier  is  subject  to  isolation  and  ostracism.  During  the  war, 
in  one  battalion,  the  men  threatened  to  kill  a  meningococcus 
carrier  who  had,  of  course  unconsciously,  infected  and  caused 
the  death  of  several  companions.  Some  individuals  cannot 
understand  the  situation  and  become  depressed  and  psychoneu- 
rotic under  quarantine  and  continued  examination.  The  circum- 
stances should  be  clearly  and  simply  explained  and  an  effort  should 
be  made  to  stimulate  the  individual's  social  morale.  His  incon- 
venience is  for  the  good  of  the  greatest  number.  In  suitable 
cases  a  radical  cure  should  be  attempted.  Otherwise  a  carrier 
should  be  instructed  in  personal  hygiene  and  be  examined  at  inter- 
vals and  inspected  for  observance  of  rules.  In  dealing  with  irre- 
sponsible persons,  forcible  detention  may  be  necessary  as  a  last 
resort. 

In  the  handling  of  carriers,  personal  hygiene  must  be  given  a 
prominent  place,  as  intelligent  cooperation  will  accomplish  results 
when  treatment  fails  or  when  quarantine  is  impossible.  The 
object  of  personal  hygiene  in  this  case  is  the  social  one  of  protecting 
others,  but  when  properly  approached,  few  individuals  will  fail 
to  respond  to  some  social  obligation. 

If  carriers  are  quarantined  in  hospitals,  the  number  may  be  so 
large  that  a  special  ward  for  isolation  and  observation  may  be 
necessary.  In  this  case  the  social  service  and  vocational  workers 
should  assist  in  keeping  up  morale.  The  "working"  quarantine 
principle  should  also  be  applied. 


40  CARRIERS   IN   INFECTIOUS   DISEASES 

Prevention.  The  prevention  of  the  development  of  carriers  is  a 
part  of  preventive  medicine,  as  well  as  their  detection  and  cure. 
Specific  measures  for  this  end  are  limited  at  present,  as  too  little 
is  known  about  the  mechanism  of  the  production  of  carriers  and 
too  few  means  of  influencing  that  mechanism  are  at  hand.  Al- 
ready, however,  we  know  that  deformities  of  the  nasal  passages 
and  the  tonsils  predispose  to  carrier  conditions.  Hence,  there  is 
an  additional  argument  for  good  hygiene  of  the  nose  and  throat. 
It  is  possible  that  in  typhoid  fever,  the  antiseptic  action  of  the 
bile  may  be  increased  by  diet  or  by  antiseptics.  It  is  also  possible 
that  the  more  severe  the  disease,  the  more  likelihood  there  is  that 
a  carrier  state  will  result.  In  this  case  there  would  be  an  extra 
argument  for  good  nursing. 

Of  course,  carriers  can  be  prevented  indirectly  by  preventing 
cases.  Carriers  can  also  be  prevented  in  a  sense  by  curing  them. 
But  the  actual  prevention  of  carriers  by  a  complete  cure  of  the 
infection  should  be  a  recognized  object  of  the  treatment  of  a  case. 
The  discharge  of  a  patient  without  release  cultures  and  appro- 
priate action  is  as  unprofessional  as  the  treatment  of  a  case  without 
a  knowledge  of  the  diagnosis. 

Altogether  the  handling  and  treatment  of  carriers  calls  for  the 
"do  the  best  you  can"  philosophy.  The  subject  is  so  full  of 
difficulties  that  the  clean  cut,  radical  and  dramatic  program,  of 
which  we  are  all  so  fond,  cannot  often  be  realized.  On  the  other 
hand,  the  actual  program  is  not  an  apologetic  one,  but  has  deep 
roots  in  evolutionary  history  and  practical  experience. 

The  present  day  efforts  at  improved  organization  and  standardi- 
zation should  include  carrier  work.  The  kind,  number  and  in- 
tervals of  diagnostic  and  release  cultures  should  be  more  uniform. 
Periods  of  isolation  and  quarantine  should  also  be  revised  in  the 
light  of  increasing  knowledge.  Most  of  all,  more  standard  and 
general  rules  for  the  handhng  and  disposition  of  carriers  are 
needed.  At  present  each  state  or  smaller  unit  has  its  own  rules 
or  no  rules,  while  what  are  needed  are  interstate  or  national 
standards.  National  medical  societies,  especially  those  devoted 
to  public  health,  have  a  responsibility  for  initiating  such  standards. 

Peterson,  Wm.  F.  :  Protein  Therapy  and  Non-specific  Resistance.     1922, 

The  Macmillan  Co.,  New  York. 
Murphy,  J.  B.,  et  al:  Jour.  Exp.  Med.,  1921,  xxxiii,  815. 
Murphy,  J.  B.,  et  al:  Jour.  Amer.  Med.  Assoc,  1921,  76,  228. 


PART  II 
SPECIAL  DISEASES 


SPECIAL  DISEASES 

In  considering  the  phorology  of  each  of  the  most  important  in- 
fectious diseases  it  is  useful  to  classify  these  diseases  according  to 
their  relation  to  the  basic  biological  necessities  of  life.  These 
necessities  are  of  course  self-preservation  and  self-pf^petuation. 
Self-preservation,  or  continued  metabolism,  calls  for  the  intake  of 
food  and  drink  and  the  excretion  of  waste  products,  for  the  intake 
of  oxygen  and  the  outgo  of  CO2,  for  the  circulation  of  these  and 
other  substances  and  for  the  control  and  correlation  of  the  vital 
reactions.  Self-perpetuation  of  course  depends  on  sexual  inter- 
course. It  also  necessitates  the  recognition  of  the  family  as  the 
primary  social  unit. 

In  the  course  of  evolution,  parasites  have  become  engrafted  on 
these  functions  and  the  carrier  aspects  naturally  form  only  a  part 
of  the  infection  as  a  whole.  The  classification  roughly  covers  the 
avenue  both  for  the  intake  and  outgo  of  the  parasite.  Thus  we 
have  alimentary,  respiratory,  circulatory  and  sexual  diseases. 
Among  the  diseases  of  the  nervous  system  or  correlating  mecha- 
nism there  are  no  clear  cut  carrier  problems  per  se  as  there  is  no 
natural  outlet.  The  "master  tissues"  are  also  well  protected 
from  direct  efforts  of  the  environment  such  as  insect  bites.  The 
advantages  of  this  grouping  are  that  similar  specimens  are  neces- 
sary for  the  diagnosis  of  carriers  and  that  similar  means  for  the 
prevention  of  carrier  action  are  used  in  each  group.  Comparison 
or  contrast  helps  to  emphasize  the  important  points. 

It  should  be  understood,  however,  that  this  classification  is 
primarily  a  practical  and  not  an  academic  one.  The  diseases 
are  not  strictly  limited  to  any  one  anatomical  or  physiological 
system.  Moreover,  the  natural  parasitic  order  is  not  observed 
as  one  and  the  same  group  may  contain  diseases  due  to  either 
bacteria,  protozoa  and  to  helminths.  In  short,  the  object  is 
practical  and  medical  rather  than  purely  scientific. 

A.  The  Alimentary  Group,  Chapters  V,  VI,  VII  and  VIII, 
includes  those  diseases  whose  parasites  enter  the  body  chiefly  in 

43 


44  CARRIERS   IN   INFECTIOUS   DISEASES 

food  and  drink  and  escape  in  the  intestinal  contents — the  typhoid 
fevers,  cholera,  the  dysenteries  and  helminthoses. 

B.  The  Respiratory  Group,  Chapters  IX,  X,  XI,  XII,  and  XIII, 
includes  the  large  number  of  diseases  whose  specific  parasites  enter 
and  escape  from  the  body  chiefly  through  the  nose  and  mouth. 
The  most  important  members  of  this  group  are  diphtheria,  men- 
ingitis, pneumonia,  influenza,  colds,  all  the  acute  exanthemata, 
pohomyelitis,  tonsillitis,  and  other  streptococcus  infections, 
Vincent's  angina,  sinusitis,  bronchitis  and  the  other  "common 
respiratory"  infections. 

C.  The  Blood  Group,  Chapter  XIV,  might  also  be  called  the 
insect  transmission  group,  as  the  parasites  live  chiefly  within  the 
blood  vessels  and  entrance  and  egress  are  possible  only  by  puncture 
of  the  vessel  wall.  It  is  desirable,  however,  not  to  confuse  insect 
carriers  with  human  carriers.  The  most  important  diseases  from 
the  carrier  point  of  view  are  malaria  and  filariasis. 

D.  The  Sexual  or  Venereal  Group,  Chapter  XV,  includes  the 
diseases  whose  parasites  enter  and  the  leave  the  body  chiefly  by 
sexual  intercourse. 


CHAPTER  V 

The  Typhoid  Fevers 

The  typhoid  fevers  inckide  the  classical  type,  the  more  recently 
differentiated  types  of  paratyphoid  A  and  B,  and  the  latest,  C. 
The  carrier  relationships  are  apparently  the  same  in  all,  with  the 
exception  of  some  forms  of  infection  with  Para  B  bacilli  which 
more  nearly  resemble  bacillary  dysentery. 

The  importance  of  carriers  in  this  group  is  well  established. 
Our  knowledge  of  carriers  was  worked  out  largely  in  typhoid  and 
there  are  on  record  many  dramatic  and  clean  cut  instances  of  the 
role  of  carriers.  The  number  of  cases  due  to  carriers  has  been 
estimated  by  different  observers  as  from  9  to  50  per  cent.  This 
percentage  is  believed  to  be  on  the  increase,  as  sanitation  and 
hygiene  are  reducing  infection  from  cases,  but  are  not  so  effective 
against  contact  infection  by  carriers. 

Carriers  are  especially  apt  to  contaminate  food  because  80  per  ' 
cent  of  carriers  are  women.    According  to  Sacquepee,  women 
make  up  only  one-fifth  of  cases,  but  three-fourths  of  intestinal 
carriers.    Carriers  among  children  are  said  to  be  rare.     Close 
contact  such   as  occurs  among  crews  on  shipboard  has  been 
especially  favorable  for  demonstrating  the  dissemination  of  bacilH 
from  a  carrier.    Urinary  carriers  are  about  one-tenth  as  frequent  • 
as  intestinal  carriers  and  apparently  occur  more  frequently  in  ''■ 
males.    Genuine   instances  of  combined  urinary  and  intestinal 
carriers  are  very  rare. 

Carriers  in  the  general  population  include  of  course  incubation- 
ary,  convalescent  and  contact  carriers.  The  relative  and  total 
number  of  these  carriers  will  depend  on  the  previous  amount  of 
typhoid;  the  age  and  sex  group,  etc.  In  general  the  number  is 
much  less  than  1  per  cent,  and  is  unquestionably  diminishing  on 
account  of  the  reduction  of  cases.  During  the  war,  the  examina- 
tion of  about  30,000  food  handlers  in  the  Army  showed  less  than 
0.1  per  cent  of  carriers  among  young  healthy  males. 


45 


46 


CARRIERS   IN   INFECTIOUS   DISEASES 


No  satisfactory  statistics  exist  on  the  relative  proportion  of 
different  kinds  of  carriers.  "Incubationary"  carriers  and  "con- 
tact" carriers  have  been  found  in  epidemics,  but  careful  clinical 
surveys,  including  the  examination  of  the  duodenal  contents,  are 
usually  lacking.  The  most  instructive  results  have  come  from  a 
study  of  convalescent  carriers.     It  has  been  estimated  by  Gay  that 


Chart  A.  Distribution  of  Typhoid  Bacilli  in  Cases  and  in  Convalescent 

Carriers 


Percentage  of  bacilli  found  in  blood     +  +  +  +  + 

Percentage  of  bacilli  found  in  urine     

Percentage  of  bacilli  found  in  feces    

Percentage  of  bacilli  found  in  duodenal  contents  — 
Percentage  of  agglutination  reactions    o-o-o-o 


THE   TYPHOID    FEVERS  47 

7500  convalescent  intestinal  carriers  are  being  yearly  added  to  the 
population  in  the  United  States. 

In  order  to  illustrate  the  percentage  of  different  kinds  of  conva- 
lescent carriers,  charts  AandB  have  been  prepared  which  show  the 
distribution  of  typhoid  bacilU  in  the  body  in  cases  and  in  temporary 


Chart  B.  Distribution  of  Typhoid  Bacilli  in  Cases  and  in 
Convalescent  Carriers 

Percentage  of  bacilli  found  in  blood     +  +  +  +  + 

Percentage  of  bacilli  found  in  urine     

Percentage  of  bacilli  found  in  feces  " 

Percentage  of  bacilli  found  in  duodenal  contents 

Percentage  of  agglutination  reactions    o-o-o-o 


48  CARRIERS   IN   INFECTIOUS   DISEASES 

and  chronic  convalescent  carriers.  The  agglutination  curve  is  also 
given.  The  data  has  been  largely  taken  from  Hiss,  Zinsser  and 
Russell's  Bacteriology,  from  Gay's  monograph  and  from  Garbat's 
recent  work  on  duodenal  cultures.  There  are  several  gaps  which 
have  been  filled  in  tentatively  from  the  author's  experience. 

As  will  be  seen,  the  charts  can  roughly  be  divided  into  four  parts. 
(1)  The  first  month  shows  the  active  case,  (2)  the  second  month 
shows  clinical  convalescence  with  the  occurrence  of  temporary 
carriers,  (3)  the  next  four  months  shows  the  spontaneous  cure  of 
many  temporary  carriers,  (4)  the  next  six  months  shows  the  per- 
sistence of  chronic  carriers  and  the  fall  of  the  agglutinative  curve 
to  a  permanent  level. 

Cultures  of  duodenal  contents  during  the  disease  have  not  been 
made  in  any  considerable  number,  but  the  percentage  of  cases 
with  bacilh  in  the  duodenum  must  be  very  high.  During  con- 
valescence, according  to  Garbat,  50  per  cent  more  carriers  are 
detected  by  this  method  than  by  ordinary  examination  of  the 
feces. 

The  curves  may  drop  slightly  after  six  months,  but  most  of 
these  chronic  carriers  persist  as  far  as  is  known  indefinitely. 
Carriers  of  at  least  thirty  years  duration  are  recorded. 

PATHOLOGY 

In  incubationary  and  pure  contact  carriers  there  is  no  definite 
carrier  lesion.  The  bacilU  live  and  multiply  in  the  intestinal 
contents  for  a  short  time,  and  then  in  the  incubationary  carrier 
invade  the  intestinal  wall  and  in  pure  contact  carriers  pass  out  of 
the  system  entirely.  Various  ingenious  theories  have  been  de- 
vised to  explain  permanent  contact  carriers,  but  a  fair  considera- 
tion of  the  lesions  will  lead  to  the  conclusion  already  expressed 
that  such  so-called  contact  carriers  are  really  convalescent  carriers 
after  mild  infections.  It  is  an  instructive  fact  that  pure  contact 
carriers  do  not  give  an  agglutination  reaction. 

In  chronic  convalescent  carriers  permanent  lesions  occur  in  the 
ducts  of  two  chief  excretory  organs,  the  liver  and  kidney.  Chronic 
inflammations  due  to  typhoid  bacilli  exist  in  other  parts  of  the 
body,  such  as  the  bones,  but  strictly  speaking  these  are  not  carrier 
lesions  because  there  is  no  natural  outlet.     It  might  be  thought 


THE   TYPHOm   FEVERS  49 

that  Peyer's  patches  would  be  a  favourable  site  for  chronic  ulcera- 
tion, but  this  is  not  the  case.  Purely  intestinal  lesions  rarely  make 
a  basis  for  carriers,  and  pathologically  the  term  "intestinal"  carrier 
should  not  be  used  unless  such  a  lesion  is  demonstrated.  The 
great  majority  of  intestinal  carriers  are  gall  bladder  or  bile  duct 
carriers.  Similarly,  from  the  pathological  point  of  view,  a  pure 
urinary  carrier  probably  does  not  occur.  There  is  a  definite  lesion 
usually  in  the  pelvis  of  the  kidney  with  secondary  pyelitis  and  cys- 
titis. Other  chronic  foci  in  the  genito-urinary  apparatus  have 
been  considered  possible  but  have  not  been  demonstrated. 

As  was  said  in  Chapter  II,  the  pathogenesis  of  these  lesions, 
especially  that  of  the  gall  bladder,  has  been  occasion  of  much 
speculation,  many  experiments  and  various  conclusions.  The 
exact  steps  of  the  process  are  not  yet  fully  agreed  upon,  but  the 
end  result  is  well  recognized.  The  explanation  is  not  entirely  an 
academic  question,  because  the  success  of  therapeutic  attack  may 
depend  on  mechanism  of  the  lesion,  whether  produced  through 
the  bile  or  through  the  blood.  In  any  case,  there  is  an  unfortu- 
nate neutralization  of  the  natural  defenses  of  the  body.  The  bile 
destroys  the  complement  and  helps  neutralize  other  antibodies 
while  the  senun  and  mucus  neutralize  any  antiseptic  action  of 
the  bile. 

These  carrier  lesions  date  back  to  the  original  attack  as  mild 
complications  which  are  usually  unnoticed.  At  autopsy  on  cases 
dying  of  toxaemia,  some  cases  of  mild  cholecystitis  are  found  with 
definitely  inflamed  waUs.  Typhoid  bacilli  are  present  in  the 
bile  in  all  cases,  but  these  early  cases  with  lesions  are  the  ones 
which  later  develop  into  carriers. 

Carrier  strains  of  the  organism  do  not  differ  in  any  known  way 
from  strains  from  cases.  There  is  no  simple  test  for  virulence  or 
pathogenicity,  but  typical  human  infections  have  occurred  from 
accidental  contamination  of  the  mouth  with  carrier  strains. 

DIAGNOSIS 

The  final  diagnosis  must  necessarily  be  made  by  laboratory 
methods,  but  the  personal  history,  a  clinical  examination,  or 
epidemiological  evidence  may  suggest  a  tentative  diagnosis. 
Many  carriers  give  a  good  history  of  the  original  attack  or  of  some 


60  CARRIERS   IN   INFECTIOUS   DISEASES 

suspicious  illness.  Some  complain  of  occasional  soreness  or  ten- 
derness over  the  gall  bladder  and  give  general  evidence  of  being 
below  par.  One  or  more  individuals  may  be  put  under  suspicion 
by  the  circumstances  of  the  epidemic. 

The  laboratory  diagnosis  is  a  bacteriological  one,  but  a  sero- 
logical examination  may  be  suggestive.  Over  50  per  cent  of  car- 
riers give  the  agglutination  test  or  Widal  reaction  as  an  indication 
of  their  chronic  forcus.  The  serum  titre  is  usually  about  1:40. 
This  test,  however,  has  httle  value  in  early  convalescents  and  in 
those  who  have  recently  been  vaccinated  against  the  disease. 

The  bacteriological  diagnosis  consists  in  isolating  and  identify- 
ing the  typhoid  organism  concerned.  Usually  the  feces  and  urine 
are  examined,.  A  single  examination  of  stool  is  not  conclusive; 
even  in  the  urine  the  findings  may  be  irregular.  A  single  examina- 
tion of  duodenal  contents  is  much  more  conclusive.  The  bacilli, 
if  present,  are  in  more  nearly  pure  culture  than  after  being  mixed 
in  the  contents  of  thirty  feet  of  intestine.  Conclusive  results  can 
be  obtained,  according  to  Garbat,  by  examining  two  consecutive 
specimens  of  duodenal  contents,  two  consecutive  specimens  of  feces 
and  two  consecutive  specimens  of  twenty-four  hour  urine. 

On  the  occurrence  of  a  case  or  cases  which  cannot  be  explained 
by  other  methods  of  infection,  a  search  for  carriers  is  indicated. 
The  circumstances  are  investigated  and,  allowing  for  the  incuba- 
tion period,  certain  suspects  are  picked  out.  The  feces  and  urine 
of  the  suspected  contacts  are  examined  once.  This  examination 
may  detect  a  carrier  who  can  then  be  further  investigated.  If 
this  examination  is  negative,  a  Widal  reaction  should  be  made, 
if  possible,  and  anyone  with  a  positive  reaction  should  be  re- 
examined by  the  duodenal  tube  method.  Any  suspects  with  a 
positive  or  doubtful  history  should  also  have  a  reexamination  of 
duodenal  contents.  Some  one  of  these  examinations  will  usually 
give  positive  results. 

In  routine  surveys,  the  feces  and  urine  of  all  individuals  should 
be  examined  once.  History  of  the  disease  should  be  inquired  into 
and  those  with  a  positive  or  doubtful  history  should  be  reexamined 
by  the  duodenal  tube  method. 


THE   TYPHOID    FEVERS  51 

SPECIMENS 

Feces.  Loose  stools  are  more  favorable  for  positive  results  as 
the  bacilli  are  brought  down  from  the  duodenum  more  rapidly. 
Calomel  has  the  reputation  of  being  a  good  cathartic  for  carrier 
specimens.  Dried  bile  is  also  used.  Individual  specimens  are 
easily  obtained  by  providing  the  patient  with  a  labelled  container 
and  directing  them  to  use  a  chamber.  A  convenient  form  of 
container  is  a  glass  vial  with  a  metal  scoop  fastened  to  the  cork. 
A  pill  box  of  tin  or  card  board  with  a  tongue  depressor  for  collec- 
tion may  also  be  used.  All  containers  should  have  a  blank  paper- 
label  for  identification  of  the  specimen.  If  the  specimen  cannot 
be  examined  within  a  few  hours,  the  vial  should  contain  a  mixture 
of  30  per  cent  glycerin  in  salt  solution  which  keeps  the  typhoid 
group  of  organisms  alive  for  a  longer  time.  One  part  of  feces 
should  be  mixed  with  about  two  parts  of  solution. 

For  collecting  large  numbers  of  specimens  more  organization  is 
necessary.  The  most  certain  method  is  to  take  the  specimen 
direct  from  the  rectum.  A  cotton  swab  is  put  into  a  piece  of 
glass  tubing  about  10  mm.  in  diameter,  the  end  of  the  tube  is 
vaselined  and  gently  forced  through  the  anus.  The  swab  is  then 
pushed  into  the  rectum,  rotated  and  withdrawn  and  put  in  a 
sterile  tube  or  in  the  glycerine  solution  mentioned  above.  The 
swab  alone  can  be  used,  if  the  cotton  is  firmly  attached  and  the 
buttocks  are  well  separated.  Care  must  be  used  not  to  break  off 
the  end  of  the  swab  in  the  rectum.  An  enema  tube  can  also  be 
used  to  advantage  as  fecal  contents  collect  in  the  opening.  Other- 
wise wooden  or  paper  plates  or  pieces  of  wood  can  be  used  to  re- 
ceive the  movement  and,  after  the  specimen  is  taken,  these  can 
be  buried  or  burned. 

Urine.  Urine  should  be  collected  in  a  small  sterile  bottle.  A 
catheterized  specimen  is  not  necessary  for  diagnosis.  Some  ob- 
servers recommend  a  specimen  from  a  mixed  twenty-four  hour 
collection.     Positive  urine  is  often  cloudy  and  very  rich  in  baciUi. 

Duodenal  contents.  This  specimen  can  be  obtained  with  less 
difficulty  than  might  be  expected.  An  Einhorn  tube,  or  modifi- 
cation, is  used  (fig.  6).  The  procedure  should  be  carried  out  on  a 
nearly  empty  stomach  and   duodenum.     The  early  morning  is 


52 


CARRIERS   IN   INFECTIOUS    DISEASES 


a  favourable  time,  after  a  light  breakfast.  The  patient  sits  up 
on  a  bed  or  couch.  The  metallic  tip  is  chilled  and  then  swallowed 
while  the  operator  gives  moral  support.  The  patient  should  then 
lie  down  on  right  side  with  knees  drawn  up  and  rest  as  the  tube 
gradually  descends.  Usually  one  to  two  hours  are  required. 
Some  workers  give  the  tube  in  the  evening  and  make  the  examina- 


FiG.  6.    Picture   of  Duodenal   Tube 
A  convenient  variety  of  the  Einhorn  Duodenal  Tube,  some  form  of 
which  is  essential  in  efficient  typhoid  carrier  work. 

tion  in  the  morning.  This  long  procedure  has  never  been  neces- 
sary in  my  hands.  A  flow  of  fluid  should  be  established  by  syphon- 
age  or  by  slight  suction  with  a  syringe.  The  first  fluid  is,  of 
course,  stomach  contents.  A  test  of  reaction  should  be  made  with 
litmus  or  better  with  methyl  red  and  phenol  red  (0.02  per  cent 


THE   TYrHOID    FEVERS  53 

watery  solution).  The  former  is  red  in  an  acid  medium  and  yellow 
in  an  alkaline  one.  With  phenol  red  the  colors  are  reversed.  As 
soon  as  a  change  occurs  in  the  color  or  consistence  of  the  flow,  a 
fresh  container  should  be  used  to  receive  the  material  and  another 
test  of  reaction  should  be  made.  Usually  when  the  duodenum 
has  been  reached  a  yellow  syrupy  fluid  appears  which  reacts  yellow 
with  methyl  red  and  red  with  phenol  red.  This  specimen  is  then 
examined  in  the  laboratory.  Naturally,  if  acid  gastric  juice  is 
submitted  for  examination,  no  information  of  value  will  be  ob- 
tained. While  the  tube  is  still  in  place,  the  Lyon  technique  can 
be  carried  out,  which  consists  in  pouring  into  the  tube,  through  a 
small  funnel,  about  30  cc.  of  a  25  per  cent  solution  of  magnesium 
sulphate.  S^^phonage  is  then  reestablished  and  frequently  a 
darker  colored  fluid  or  "B"  bile  is  obtained.  If  this  is  really  gall 
bladder  bile,  it  would  be  preferable  to  plain  duodenal  contents, 
but  as  duodenal  contents  are  usually  satisfactory  and  there  is 
doubt  about  the  origin  of  B  bile,  this  procedure  for  carrier  work  is 
an  unnecessarj^  refinement. 

TECHNIQUE 

The  duodenal  contents  are  spread  directly  on  Endo  plates. 
Some  of  the  specimen  should  also  be  incubated  for  twenty-four 
hours  and  other  plates  inoculated.  A  microscopic  examination  of 
the  centrifuged  sediment  may  show  leucocytes  in  positive  cases. 
The  further  procedure  is  given  below. 

A  drop  of  liquid  feces  or  a  mixture  of  hard  feces  in  broth  is 
spread  on  the  surface  of  differential  media  and  search  made  for 
colonies  characteristic  of  the  typhoid  group.  Only  by  experience 
can  the  proper  amount  of  inoculum  be  judged.  It  is  best  to  use 
several  plates  and  the  usual  trouble  is  too  many  rather  than  too' 
few  colonies.  Some  workers  enrich  specimens  with  dilutions  of 
brilliant  green.  This  method  succeeds  at  times,  but  fails  at  others. 
If  the  time  which  the  bacteriologist  might  devote  to  enrichment 
were  spent  in  securing  specimens  of  duodenal  contents,  the  end 
results  would  be  much  better.  Many  differential  media  have  been 
proposed,  such  as  lactose  litmus  agar,  eosin  methylene  blue  agar, 
malachite  green,  phenol  red  or  brom  cresol  purple  media.  All 
have  their  merits  and  drawbacks.     In  the  Army  Medical  School 


54  CARRIERS   IN   INFECTIOUS    DISEASES 

method,  worked  out  by  Russell,  Endo  medium  is  used  and  in  spite 
of  some  drawbacks,  is  most  serviceable.  As  it  rapidly  deteriorates, 
the  ingredients  are  kept  separatel}^ — 3  per  cent  extract  agar,  pH 
7.8,  is  kept  in  flasks  and  sterile  solutions  are  prepared  of  10  per  cent 
lactose,  saturated  alcoholic  solution  of  basic  fuchsin  and  10  per 
cent  watery  sodium  sulphite.  A  few  hours  before  use,  the  agar 
is  melted,  and  the  ingredients  are  added — 1  per  cent  lactose,  1.8  cc, 
fuchsin  and  about  25  cc.  sulphite  to  the  liter.  The  agar  should 
then  be  cooled  to  about  50°  and  poured  into  Petri  dishes,  small  or 
large.  The  agar  is  allowed  to  harden  with  the  cover  ajar  in  a 
dust  free  place.  The  specimen  is  then  spread  with  a  loop  or  a 
right  angle  glass  spreader.  Incubate  twenty-four  hours  and  ex- 
amine for  colorless,  translucent,  non-lactose  fermenting  colonies. 
Mark  and  transfer  several  to  Russell  double  sugar  tubes,  inoculat- 
ing l)oth  butt  and  slant  (3  per  cent  agar  with  1  per  cent  lactose, 
0.1  per  cent  glucose,  pH  7.6  and  phenol  red  as  an  indicator).  If 
the  colonies  are  numerous  enough,  agglutination  can  be  done 
immediately  with  colonies  made  up  of  small  Gram  negative 
bacilli. 

The  double  sugar  tubes  are  incubated  for  twenty-four  hours  and 
are  then  examined  for  characteristic  appearance  of  the  typhoid 
group.  This  for  the  typhoid  bacillus  is  an  acid  butt  with  no  gas 
bubbles  and  an  alkaline  slant.  With  Para  A  or  B,  the  butt  is 
acid  and  broken  up  with  gas  bubbles  and  the  slant  is  alkaline, 
especially  so  with  Para  B.  Colon  bacilli  produce  more  gas  in  the 
butt  and  an  acid  slant,  which,  however,  may  turn  alkaline  in  case 
of  B.  aerogenes. 

Growth  from  typical  double  sugar  tubes  are  stained  and  if 
Gram  negative  bacilli  are  found,  agglutination  is  done  with  spe- 
cific sera  by  transferring  a  suspension  or  a  loopful  to  different  dilu- 
tions of  serum.  If  satisfactory  agglutination  and  controls  result, 
the  diagnosis  is  made.  The  culture  should  be  plated  out  and  a 
pure  culture  kept  for  reference  or  confirmation. 

The  urine  is  plated  direct  in  liberal  quantity  and  also  incubated 
in  about  five  parts  of  broth  and  plated  again  after  twenty-four 
hours.  The  growth  of  bacilli  in  carriers  is  often  rich  and  pure. 
Occasionall}^  excretion  is  periodic. 


THE   TYPHOID    FEVERS  55 

As  soon  as  the  bacteriological  diagnosis  is  made  a  further  clinical 
diagnosis  of  the  location  of  the  focus  is  necessary.  This  involves 
examination  of  specimens  from  the  duodenal  contents  if  not  al- 
ready made  and  cultures  after  ureteral  catheterization  in  case  of 
urinary  carriers.  A  diagnosis  of  biliary  passage  lesion  can  be 
made  if  the  duodenal  contents  are  positive,  but  whether  the  focus 
is  confined  to  the  gall  bladder  or  whether  it  also  occurs  in  the 
liver  cannot  be  told,  except  as  a  result  of  operation.  An  X-ray 
picture  may  assist  in  locating  the  lesion  in  a  urinary  carrier,  as  it 
is  usually  a  unilateral  pyelitis. 

A  diagnosis  of  the  kind  of  carrier  should  also  be  made,  whether 
convalescent  or  contact,  based  on  the  history  and  probabilities  of 
slight  illness.  The  epidemiological  significance  of  the  carrier 
should  also  be  looked  into,  such  as  history  of  occurrence  of  pre- 
vious cases  among  his  contacts,  and  so  forth. 

TREATMENT 

After  a  thorough  diagnosis  is  made,  further  spread  of  bacilli 
should  be  prevented  as  far  as  possible  by  insisting  on  good  personal 
hygiene  of  the  carrier.  If  the  carrier  will  not  observe  rules  or  is 
an  old  offender,  quarantine  may  be  enforced  with  legal  sanction 
in  many  places.  Under  these  circumstances  the  carrier  is  more 
apt  to  agree  to  radical  treatment. 

In  the  technical  treatment,  surgical  measures  are  the  most 
effective.  The  focus  in  many  carriers  is  a  single  local  one  which 
can  be  cured  by  excision.  Thus  many  carriers  have  been  cured 
by  cholecystectomy  and  nephrectomy.  Unfortunately,  in  some 
cases  the  foci  are  multiple,  especially  in  the  biliary  tract  and  ex- 
cision of  one  focus  does  not  cure  the  condition.  Such  carriers  can 
be  determined  only  by  operation  and  are  incurable  at  present,  but 
probably  form  the  minority.  Cholecystectomy  should,  therefore, 
be  tried  in  all  cases  possible.  Cholecystectomy  with  hepatic  drain- 
age has  been  advised  for  liver  carrieip.  Ilhistrative  specimens  are 
given  in  figures  7,  8,  and  9. 

The  technical  details  of  the  operation  cannot  be  discussed  here, 
but  the  situation  calls  for  cooperation  on  part  of  the  surgeon. 
The  diagnosis,  made  by  the  internist  or  pathologist,  must  be 
accepted  without   clinical  evidence.     Especial  effort  should  be 


56 


CARRIERS   IN    INFECTIOUS    DISEASES 


made  not  to  damage  the  individual.  In  convalescent  cases, 
operation  should  not  be  performed  until  at  least  six  months  after 
recovery,  as  some  cases  will  spontaneously  clear  up  during  this 
interval. 


« 


Fig.  7.  Gall  Bladder  and  Gall  Stone  from  a  Typhoid  Carrier  Re- 
moved AT  Operation  Seven  Years  after  Original  Attack 
Carrier  was  a  member  of  the  Army  Nurse  Corps.     Operation  cured  the 
carrier  condition.     (Reprinted  with  permission  from  Journal  of  the  Ameri- 
can Medical  Association .) 

Many  other  methods  of  treatment  have  been  tried  and  some 
partial  success  apparentl}^  has  been  obtained,  but  the  results  are 
so  irregular,  compared  with  those  of  surgical  treatment,  that 
coincidence  may  explain  them.     (See  Chapter  IV.) 


THE   TYPHOID    FEVERS 


57 


Fig.  8.  Gall  Bladder  and  Gall  Stones  from  a  Typhoid  Carrier  Re- 
moved AT  Operation  Seven  Years  After  Original  Attack 
Carrier  was  an  army  cook  who  was  detected  by  routine  examination  of 
food  handlers.    Operation  did  not  cure  the  carrier  state. 


58 


CARRIERS    IN    INFECTIOUS    DISEASES 


THE   TYPHOID    FEVERS 


59 


Gay,  F.  p.  :  Typhoid  Fever.     1918,  Macmillan  Company. 

Garbat  a   L.:  Monographs  of  the  Rockefeller  Institute.     1922.    No.  16. 

Nichols,  H.  J.,  Simmons,  J.  S.,  and  Stimmel,  C.  O.:  Jour.  Amer.  Med. 

Assoc,  1919,  Ixxiii,  680. 
Henes,  H.,  Jr.:  Jour.  Amer.  Med.  Assoc,  1920,  Ixxv,  1771. 


CHAPTER  VI 

Cholera 

Next  to  the  discovery  of  the  cholera  vibrio  in  the  intestinal 
tract  of  patients,  the  recognition  of  a  chronic  cholecystitis  as  a 
focus  of  the  carrier  state  was  the  most  important  advance  in  the 
possibiHties  of  control  of  this  disease.  The  carrier  conception  was 
first  reached  in  the  study  of  cholera,  but  the  practical  consequences 
of  this  discovery  were  not  generally  realized  until  a  pathological 
basis  for  the  existence  of  carriers  was  established.  Cholera  in 
endemic  centers  occurs  with  distant  seasonal  regularity.  There 
are  intervals  of  complete  freedom  from  the  disease.  The  where- 
abouts of  the  vibrio  in  this  interval  was  a  mystery  until  a  chronic 
cholecystitis  was  recognized.  Much  ingenuity  was  expended  on 
possible  life  cycles  in  the  environment,  but,  as  is  frequently  the 
case  in  the  infectious  diseases,  the  trouble  was  found  closer  home. 
The  carrier  is  now  believed  to  be  the  real  reservoir  of  the  disease 
from  year  to  year.  While  the  acute  case  causes  most  other  cases 
during  an  epidemic,  the  carrier  causes  the  epidemic  itself.  The 
carrier  problem  in  cholera  is  most  difficult  in  endemic  centers  as 
the  natives  have  racial  and  reHgious  prejudices  and  personal 
habits  which  are  foreign  to  scientific  medicine.  On  the  other 
hand,  where  bacteriological  examinations  and  quarantine  can  be 
enforced,  as  in  the  case  of  emigrants,  it  has  been  shown  by  the 
Public  Health  Service  that  wholesale  carrier  work  is  possible  and 
is  effective  in  protecting  the  country  from  cholera.  Most  of  the 
recent  work  in  the  prevention  of  cholera  in  India  (Grieg)  and  in 
the  Philippines  (McLaughlin,  Munson)  has  been  along  carrier 
lines. 

Incubationary  carriers  are  known  who  pass  vibrios  in  the  stools 
for  days  or  weeks  and  finally  develop  the  disease.  Digestive 
upsets  from  irritating  food  or  catharsis  may  precipitate  the 
attack.  Such  cases  can  be  distinguished  from  contact  carriers 
only  by  the  outcome,  as  no  test  of  immunity  is  available. 

As  in  the  case  of  typhoid,  the  number  of  organisms  in  the  body 
become  rapidly  reduced  in  most  cases  within  the  time  of  clinical 


CHOLERA  61 

recovery.  A  small  number,  about  3  per  cent,  do,  however,  be- 
come convalescent  carriers  and  reservoirs  of  infection.  These 
carriers  are  apparently  not  as  persistent  as  typhoid  carriers,  but 
final  statements  can  not  be  made  on  this  subject  until  more  work 
is  done  on  cultures  of  duodenal  contents  in  life  and  on  gall  bladder 
contents  at  operation  and  autopsy. 

Contact  carriers  are  still  more  temporary.  They  may  be  as 
numerous  as  6  to  30  per  cent.  Care  is  necessary  to  rule  out  mild 
infections. 

PATHOLOGY 

As  in  the  case  of  faecal  typhoid  carriers,  a  focus  is  found  in 
the  gall  bladder.  This  consists  of  a  mild  catarrhal  inflammation 
which  gives  no  clinical  symptoms  and  is  discovered  only  by  in- 
ference after  bacteriological  examination  or  at  autopsy.  It  is  not 
known  whether  lesions  occur  in  other  parts  of  the  biliary  system. 
Although  the  subject  has  not  been  as  fully  worked  out  as  in  typhoid 
carriers,  the  high  percentage  of  positive  findings  in  the  bile  strongly 
suggest  that  the  cholecystitis  is  the  principal  carrier  focus. 

There  is  no  general  agreement  as  to  the  pathogenesis  of  this 
lesion.  Some  observers  favor  the  theory  of  ascending  infection 
through  the  common  duct,  others  (Greig),  infection  through  the 
lymphatics.  Cholera  vibrios  do  not  invade  the  blood  to  the  same 
extent  as  typhoid  bacilli,  but  they  are  not  confined  as  strictly  to  the 
intestinal  tract  as  was  once  thought,  because  they  have  been 
found  in  the  urine  during  hfe  and  in  the  lungs  at  autopsy.  A 
theory  of  portal  system  septicaemia  with  excretion  of  the  vibrios 
through  the  bile  has  been  advanced  by  the  author  to  account  for 
the  cholecystitis.  In  any  case,  the  lesion  occurs  and  lasts  for  an 
indefinite  time.  Further  work  along  these  lines  is  much  needed. 
An  experimental  cholecystitis  can  be  reproduced  experimentally 
in  rabbits  and  especially  in  guinea  pigs  by  intravenous  injection 
or  direct  inoculation  (Schobl). 

Carrier  strains  of  the  vibrio  have  been  studied  from  the  com- 
parative point  of  view  and  no  differences  have  been  noted  as  com- 
pared with  strains  from  cases.  Atypical  strains,  however,  are 
especially  apt  to  be  troublesome.  They  may  not  agglutinate  and 
their  significance  remains  uncertain. 


62  CARRIERS   IN   INFECTIOUS   DISEASES 

DIAGNOSIS 

The  same  general  rules  apply  as  in  typhoid  carriers.  The 
final  diagnosis  is  bacteriological,  but  the  personal  history  and 
epidemiological  circumstances  may  assist  in  the  detection.  Sero- 
agglutination  may  also  be  of  value  in  some  instances. 

Cultures  of  duodenal  contents  of  suspected  carriers  have  ap- 
parently not  yet  been  made  on  any  scale,  but  the  information 
which  can  be  gained  in  this  way  would  be  very  valuable  from 
many  points  of  view. 

The  specimens  of  feces  are  collected  in  the  same  way  as  in  ty- 
phoid carrier  work.  As  large  numbers  of  persons  must  often  be 
examined  in  a  short  time,  an  organization  of  the  work  is  necessary. 

TECHNIQUE 

The  principle  of  diagnosis  is  to  isolate  a  vibrio  which  aggluti- 
nates with  a  specific  serum.  The  special  points,  in  the  isolation,  are 
the  use  of  enrichment  and  a  selective  medium  which  favors  the 
development  of  the  vibrio  and  inhibits  other  organisms.  A  rectal 
swab  or  small  amount  of  feces  is  enriched  in  alkaline  peptone  water, 
pH  8.4,  for  several  hours.  A  transfer  from  the  surface  is  then  made 
to  a  second  tube.  After  six  hours  the  surface  growth  is  spread 
on  alkaline  agar,  pH  8.4  (faintly  alkaline  to  phenolphthalein). 
This  medium  allows  a  good  growth  of  the  vibrios  in  translucent 
colonies.  Material  from  the  suspicious  colonies  is  stained  with 
dilute  carbol  fuchsin  and  examined  for  vibrios.  If  present,  a 
micro-agglutination  is  made  with  standard  anti-cholera  serum,  or  a 
transfer  is  made  to  alkaline  agar  and  a  macro-agglutination  is  made 
the  next  day.  If  the  reaction  is  clear  cut,  a  diagnosis  can  be  made. 
A  transfer  of  the  culture  should  be  saved  for  confirmation.  Some 
typical  vibrios  do  not  agglutinate  well  at  first.  Further  cultural 
and  serological  work  is  necessary.  There  are  many  unsettled 
problems  of  strains  of  vibrios  which  apply  to  carrier  as  weU  as 
clinical  work.     No  reliable  virulence  test  is  available. 

A  great  many  differential  and  special  media  have  been  devised 
for  cholera  work.  In  general,  the  simplest  is  the  best,  and  the 
above  outline  will  give  good  results. 


CHOLEBA  63 

When  carriers  have  been  found,  an  effort  should  be  made  by 
the  history  and  by  further  examinations  to  classify  the  carrier 
and  to  determine  the  social  bearings  of  the  condition. 

TREATMENT 

The  first  measure  is  isolation  and  instruction  in  personal  hygiene. 
Intestinal  upsets  should  be  avoided  as  they  may  precipitate  an 
attack  in  an  incubationary  carrier.  Many  carriers  are  relatively 
of  short  duration  and  will  clear  up  while  under  observation.  For 
chronic  carriers,  as  in  typhoid,  many  measures  have  been  tried, 
but  with  irregular  results.  In  long  term  chronic  carriers,  surgical 
measures  should  be  considered. 

Greig,  E.  D.  W.  :  Ind.  Jour.  Med.  Res.     1913-4,  i,  44,  59;  1914-15,  ii,  1,  28, 

907;  1916,  iii,  259. 
ScHOBL,  O.:  Phil.  Jour.  Sc,  1915,  B.,  x,  11;  Jour.  Inf.  Dis.,  1916,  xviii,  307. 
McLaughlin,  A.  J.:  N.  Y.  Med.  Jour.,  1909,  xc,  1116. 


CHAPTER  VII 

The  Dysenteries 
a.  bacillary  dysentery 

The  carrier  is  apparently  of  less  importance  in  the  spread  of 
dysentery  than  in  the  spread  of  typhoid  or  cholera.  There  are 
fewer  true  carriers  and  the  individual  carrier  is  less  chronic  and 
excretes  fewer  bacilli.  Acute  and  chronic  cases  are  usually  re- 
sponsible for  spreading  infection.  On  the  other  hand,  definite 
instances  are  recorded  of  spread  of  this  serious  disease  through 
apparently  healthy  carriers. 

Incubationary  carriers  are  known.  In  the  absence  of  a  test 
for  susceptibility  and  in  view  of  the  relapsing  character  of  the 
attack,  it  is  difficult  to  diagnose  such  carriers  except  by  careful 
consideration  of  the  previous  history  and  subsequent  course. 

In  temporary  convalescent  carriers,  the  curve  representing  the 
presence  of  bacilli  in  the  feces  falls  gradually  after  clinical  recovery, 
but  does  not  reach  a  low  percentage  for  about  two  months.  Re- 
peated examinations  are  necessary  to  exclude  the  carrier  state. 

Chronic  convalescent  carriers,  running  up  to  a  year,  occur  in  1 
to  5  per  cent  in  different  series.  It  is  difficult  to  draw  the  line 
between  relapsing  carriers  and  chronic  cases.  Flexner  bacillus 
infections  are  more  apt  to  result  in  carriers,  while  Shiga  bacillus 
infections  are  more  apt  to  be  chronic  cases. 

Contact  carriers  have  usually  been  considered  as  rare,  but  with 
improvement  in  technique  of  examination,  are  found  more  fre- 
quently. Here  again  the  exact  diagnosis  is  difficult  between  a 
convalescent  carrier  after  a  mild  case  and  a  true  contact  carrier 
who  has  never  been  sick. 

Pathology 

In  the  true  contact  carrier  the  bacilh  apparently  have  no  focus 
and  live  for  a  short  time  in  the  lumen  of  the  colon. 

64 


THE   DYSENTERIES  65 

In  the  convalescent  carrier  the  lesion  is  an  ulcer  of  the  original 
attack  which  has  failed  to  heal  with  the  establishment  of  a  general 
immunity.  The  ulcers  of  bacillary  dysentery  have  characteristic 
differences  from  amoebic  ulcers.  They  usually  run  transversely, 
are  superficial  and  occur  in  the  ileum  as  well  as  the  caecum. 
Dysentery  baciUi  apparently  do  not  regularly  invade  the  blood 
and  other  foci,  as  in  the  gall  bladder,  are  rare.  Urinary  carriers 
are  unknown. 

Diagnosis 

The  personal  history  of  intestinal  trouble  and  of  residence  in 
infected  regions  may  be  suggestive.  The  presence  of  mucous  in 
the  stool  is  suspicious.    Epidemiological  data  are  also  often  useful. 

In  the  laboratory  diagnosis,  the  finding  of  the  organism  is  of 
course  the  main  object,  but  examination  of  the  blood  serum  for 
agglutination  may  be  of  much  assistance  and  sometimes  a  pre- 
sumptive diagnosis  must  be  made  on  agglutination  alone.  The 
agglutination  curve  usually  falls  promptly  after  convalescence 
and  its  persistence  in  strength  up  to  1-50,  or  1-100  is  very  sus- 
picious, especially  in  view  of  the  difficulties  of  stool  examination. 

Technique 

The  general  rules  given  for  the  examination  of  feces  of  suspected 
typhoid  carriers  apply  here.  Examination  of  the  rectum  with  a 
protoscope  sometimes  reveals  an  ulcer  which  can  be  cultured 
directly.  In  the  stool  mucous  should  be  sought  for  and  plated 
on  several  plates,  A  great  many  media  have  been  used.  Lactose 
litmus  agar  is  one  of  the  simplest  and  best.  Endo  medium  should 
be  used,  but  is  not  favourable  for  the  growth  of  the  Shiga  bacillus. 

The  plates  after  incubation  are  examined  for  non-lactose  fer- 
menting colonies  and  transfers  are  made  to  Russell  double  or 
triple  sugar  in  the  regular  way.  The  reactions  in  the  Russell  tube 
are  identical  with  those  of  typhoid  bacillus.  There  is  an  acid 
butt  with  no  bubbles  of  gas  and  an  alkahne  slant.  If  typical 
growths  in  the  tubes  show  on  staining  a  Gram  negative  bacillus, 
agglutination  is  done  with  monovalent  sera  at  a  strength  corre- 
sponding to  the  titre.  There  are  a  number  of  organisms  whose 
significance  in  actual  dysentery  is  uncertain  and  the  same  is  true 


66  CARRIERS   IN   INFECTIOUS   DISEASES 

in  carrier  work.  If  an  organism  is  isolated  it  should  be  aggluti- 
nated with  the  individual's  serum  for  additional  data.  A  nega- 
tive reaction  would  tend  to  rule  out  a  convalescent  carrier,  but  not 
a  contact  carrier.  At  least  three  release  cultures  should  be  made 
over  two  or  three  weeks  as  the  bacilli  are  hard  to  find. 

Treatment 

The  field  of  specific  treatment  with  serum  vaccines  has  not  been 
thoroughly  explored,  but  is  not  promising.  If  the  ulcer  is  in  the 
rectum  alone  local  treatment  is  effective.  Usually  the  most  that 
can  be  done  is  general  hygienic  treatment  with  lavage  of  the 
colon.  Instruction  in  personal  hygiene  should  be  given.  Con- 
tinued observation  is  necessary. 

Medical  Research  Committee.    London,  Special  Reports  Nos.  7  and  40. 
B.    PROTOZOAL  DYSENTERIES 

1.  Amoebic  dysentery 

The  pathogenic  amoeba,  Endamoeba  histolytica,  is  not  limited 
to  the  tropics  as  closely  as  was  formerly  thought  and  amoebic 
dysentery,  or  more  properly  amoebiasis,  is  a  serious  cause  of  ill 
health  in  many  parts  of  the  world.  Amoebiasis  is  the  better 
term  as  dysenteric  symptoms  may  be  slight  or  absent  and  the 
principal  damage  may  be  anemia,  neurasthenia,  or  liver  abscess. 
In  the  spread  of  this  infection  carriers  play  an  important  part. 
In  fact,  the  cyst,  which  is  the  only  infecting  stage  in  the  Hfe  cycle 
of  the  amoeba,  is  characteristic  of  carriers  rather  than  of  cases, 
as  its  presence  indicates  that  a  balance  is  being  reached.  The 
vegetative  forms,  which  produce  the  symptoms,  are  not  infective. 
From  the  point  of  view  of  the  parasite,  therefore,  the  transmission 
of  the  disease  is  due  to  a  carrier  stage  in  100  per  cent  of  instances. 
In  the  acute  stages  of  the  infection,  cysts  are  not  found  as  fre- 
quently as  in  the  chronic  stages.  It  may  be  difficult  at  times  to 
differentiate  a  chronic  case  from  a  true  carrier,  as  cases  merge  into 
carriers  and  carriers  into  relapsing  cases;  but  true  carriers  do 
exist,  with  a  limited  active  focus  and  many  cysts.  The  immunity 
in  such  protozoal  diseases  is  not  as  clear  cut  as  in  bacterial  diseases. 
A  balance  is  more  easily  reached  and  with  less  evidence  of  infection. 


THE   DYSENTERIES  67 

The  percentage  of  temporary  convalescent  carriers  is  very 
high.  On  the  Mexican  border  in  1916-1917,  Craig  found  that  of 
115  cases,  86,  or  about  75  per  cent,  developed  cysts  and  became 
at  least  temporary  convalescent  carriers.  The  further  history  of 
such  carriers  is  not  entirely  known.  Spontaneous  cure  of  some 
cases  and  carriers  undoubtedly  occurs,  but  even  with  the  best 
treatment  about  10  per  cent  may  remain  carriers.  The  percent- 
age of  so-called  contact  carriers  is  said  to  be  much  more  numerous 
than  convalescent  carriers,  but  the  possibility  of  a  mild  or  atypical 
attack  is  to  be  kept  in  mind.  In  the  general  population,  carriers 
are  of  course  most  prevalent  in  endemic  centers  in  the  tropics  and 
least  in  temperate  regions.  Thus,  Young,  in  Manaos,  Brazil, 
found  no  less  than  27.5  per  cent  of  native  troops,  apparently  in 
good  health,  harboring  cysts  of  Endamoeba  histolytica,  whereas 
among  army  recruits  in  England,  Mathews  and  Smith  found  only 
5.6  per  cent  carriers.  The  possibilities  of  carrier  infection  through 
food  handled  by  careless  and  ignorant  native  servants  have  often 
been  realized. 

Pathology.  In  the  chronic  convalescent  carrier  the  lesion  is  an 
unhealed  ulcer  of  the  colon.  Here  the  vegetative  forms  of  the 
parasite  persist  and  produce  cysts.  This  cyst  cannot  reproduce 
itself  and  the  vegetative  form  cannot  live  long  in  the  intestinal 
contents.  It  requires  some  focus  or  home  in  the  intestinal  wall. 
Hence,  the  pure  contact  carrier  is  very  temporary.  So-called 
chronic  contact  carriers  are  either  mild  chronic  cases  or  convales- 
cent carriers  from  mild  infections. 

Chronic  foci  occur  in  other  parts  of  the  body,  as  abscesses,  but 
usually  have  no  natural  outlet.  One  case  of  gall  bladder  lesion  has 
come  to  the  writer's  notice.  The  patient,  a  medical  officer,  had 
an  enlarged  gall  bladder  and  incidentally  was  an  amoebic  carrier. 
The  gall  bladder  on  removal  had  a  thick  leathery  wall.  The 
contents  were  purulent  and  showed  many  active  amoebae.  Amoe- 
bae were  also  found  later  in  the  wall  by  section.  Soon  after  opera- 
tion he  was  free  from  the  carrier  state.  This  condition  is  possibly 
not  as  unusual  as  it  seems. 

Diagnosis.  This  is  made  by  the  microscope.  No  serological 
reactions  are  available.  Clinical  history  and  circumstances  may 
be  suggestive.    A  formed  stool  is  preferable  for  looking  for  cysts. 


D»  CARRIERS   IN   INFECTIOUS   DISEASES 

Frequently  a  diagnosis  can  be  made  with  the  fresh  specimen  by 
finding  of  four  nucleated  round  or  oval  cysts.  In  general,  how- 
ever, on  account  of  the  frequent  presence  of  other  .cysts  in  the 
feces,  it  is  preferable  to  have  stained  specimens  examined  by  an 
experienced  worker.  Differentiation  must  be  made  from  cysts 
of  the  harmless  amoeba  and  those  of  other  protozoa.  Occasionally 
material  can  be  obtained  directly  from  a  rectal  ulcer.  A  single 
examination  will  detect  only  about  one-third  of  carriers. 

In  the  examination  of  large  numbers  of  individuals,  which  must 
be  made  if  the  carrier  program  is  to  yield  results,  some  organiza- 
tion is  necessary.  Specimens  must  be  properly  collected,  labelled, 
and  so  forth,  as  was  emphasized  under  discussion  of  specimens 
for  typhoid  carriers. 

Treatment.  The  treatment  is  that  for  the  original  infection  and 
must  be  directed  both  against  the  vegetative  forms  in  the  tissue 
and  the  cysts  in  the  feces.  Emetin  is  best  for  the  tissue  infection. 
Hypodermic  injections  in  courses  are  given  of  |  to  1  grain  a  day 
for  seven  days  with  a  short  rest  and  repetition.  Toxic  sjmaptoms 
must  be  watched  for  such  as  neuritis,  especially  of  the  legs,  and 
myocarditis.  The  cysts  in  the  feces  can  be  reduced  by  large  doses 
of  bismuth  subnitrate,  one  heaping  teaspoonful  in  one-half  glass 
of  water  before  meals.  Emetin  bismuth  iodide  by  mouth  has 
advantages  in  both  directions,  but  it  is  apt  to  nauseate.  Courses 
of  3  grains  daily  for  twelve  days  cured  91  per  cent  of  cases  in  the 
Enghsh  experience.  Colon  lavage  with  quinine  1 :  1000,  or  argyrol 
is  of  value. 

Repeated  negative  examinations  are  necessary  for  release  as 
single  examinations  are  inadequate. 

Carriers  should  be  instructed  in  personal  hygiene  and  kept 
in  quarantine  if  not  too  numerous.  If  the  nmnber  is  too  large 
for  quarantine,  personal  hygiene  and  sanitation  must  be  depended 


2.  Other  -protozoal  dysenteries 

True  carriers  are  definitely  known  in  one  other  form  of  proto- 
zoal dysentery,  namely,  Balantidiosis.  The  disease  is  compara- 
tively rare.  The  carrier  relationships  are  much  the  same  as  in 
amoebiasis.     The  vegetative  forms  live  in  ulcers  in  the  wall  of  the 


THE   DYSENTERIES  69 

intestine  and  form  cysts  which  are  excreted  and  are  infective.  It 
is  possible  that  the  vegetative  forms  can  Uve  some  time  in  the 
feces  and  encyst  there.  If  this  is  so,  true  contact  carriers  would 
have  more  of  a  place  than  in  amoebic  dysentery.  The  pig,  a 
common  scavenger  in  the  tropics,  is  infected  with  a  similar 
parasite. 

Emetine  and  arsphenamine  should  be  tried  in  treatment. 

Besides  these  true  carriers,  there  are  a  large  number  of  possible 
carriers  of  other  protozoa,  such  as  trichomonads,  lamblia,  et 
cetera,  whose  clinical  significance  is  not  yet  well  understood.  They 
maj^  be  primarily  pathogenic  in  some  cases,  or  they  may  be  purely 
secondary  or  saphrophytic.  Giardia  intestinalis  is  generally  re- 
garded as  pathogenic,  but  there  is  considerable  doubt  about  the 
importance  of  other  protozoa.  The  carriers  of  most  of  them  are 
probable  pseudo  carriers. 

In  all  these  conditions,  with  the  possible  exception  of  tricho- 
monas infections,  the  cyst  stage  of  the  parasite  occurs  as  the  basis 
of  a  possible  carrier  state. 

In  Giardia  infections,  it  is  often  difficult  to  differentiate  a  case 
from  a  carrier  as  the  symptoms  in  a  case  may  be  mild  and  indefinite. 
The  lesion  is  in  the  duodenum  where  the  parasites  become  at- 
tached to  the  mucous  membrane.  True  carriers  are  either  immune 
or  slightly  infected. 

The  diagnosis  is  made  on  the  absence  of  definite  symptoms  and 
the  finding  of  cysts  in  the  intestinal  contents.  The  duodenal  tube 
has  been  used  to  good  advantage  as  motile  fonns  have  been  found 
in  duodenal  contents  when  the  feces  were  negative  or  showed 
only  a  few  cysts. 

The  diagnosis  of  carriers  of  intestinal  protozoa  requires  con- 
siderable experience  and  technique.  A  large  number  of  cysts 
or  cyst-like  bodies  occur  in  feces  and  frequent  errors  in  interpre- 
tation have  been  made  which  vitiate  many  diagnoses  and  sets  of 
statistics. 

Medical  Research  Committee.    London,  Special  Reports  Nos.  4,  15,  29. 
DoBELL,  Clifford,  and  O'Connor,  F.  W.  :  The   Intestinal  Protozoa  of 

Man.    Wm.  Wood  &  Co.,  1921. 
Craig,  C.  F.:  Military  Surgeon,  1917,  March  and  April. 


CHAPTER  VIII 

Helminthoses 

Carriers  of  helminths  are  recognized  and  play  a  definite  part 
in  the  spread  of  diseases  due  to  worms.  They  are  not  dangerous 
to  their  inmiediate  contacts,  like  the  intestinal  carriers  so  far 
considered,  as  the  parasites  must  develop  outside  the  body  before 
infection  is  possible.  The  carrier,  therefore,  infects  only  his 
environment  and  is  most  important  in  warm  parts  of  the  earth 
where  the  population  lives  close  to  the  soil. 

In  these  infections  it  may  be  especially  difficult  to  distinguish 
between  cases  and  carriers.  A  person  may  become  immunized  to 
the  effect  of  the  parasite  and  thus  be  a  true  carrier,  but  usually 
a  carrier  is  one  who  has  not  enough  parasites  to  be  a  case.  Thus, 
in  hookworm  infections,  the  number  of  worms  necessary  to  pro- 
duce any  real  disease  is  put  at  10  to  100  or  more  by  different 
authors.  A  person  with  a  few  worms  would  thus  be  a  carrier. 
While  from  the  theoretical  standpoint  it  is  very  desirable  to  have 
well  defined  standards  of  cases  and  carriers,  it  is  a  mistake,  from 
the  practical  point  of  view,  to  split  hairs  over  the  diagnosis. 

While  carriers  usually  infect  their  environment  less  than  cases, 
a  continued  small  infection  will  in  time  be  as  bad  as  a  single  mas- 
sive infection. 

Carriers  in  hookworm  infections  will  be  described  as  typical  of 
this  group  because  this  infection  is  best  known  and  other  less  well 
known  diseases  seem  to  be  similar  in  general. 

Carriers  are  very  prevalent  in  infected  regions.  A  large  per- 
centage of  persons  excrete  ova  but  only  a  few  will  show  symptoms. 
Hence,  the  carrier  is  a  real  problem. 

PATHOLOGY 

The  carrier  lesion  is  the  same  as  the  case  lesion.  The  worms 
attach  themselves  to  the  mucous  membrane  of  the  ileum  and 
feed  on  bits  of  tissues  and  tissue  juices.  Their  number  is  so  small, 
however,  that  they  do  no  general  damage.  They  may  live  for 
a  time  free  in  the  lumen  like  other  round  worms. 

70 


HELMINTHOSES  71 

DIAGNOSIS 

Residence  in  an  endemic  area  is  suggestive  and  history  of  ex- 
posure to  skin  infection  or  of  ground  itch  may  be  obtained.  Ex- 
amination of  blood  for  eosinophilia  may  also  be  suggestive.  The 
final  diagnosis  depends  on  finding  ova  or  worms  in  the  stool. 

It  has  been  found  that  the  number  of  ova  in  the  stool  is  roughly 
an  index  of  the  number  of  worms  present.  If  we,  therefore,  adopt 
as  a  standard  of  carrier  state,  10  to  100  worms,  the  condition  can 
be  diagnosed  by  less  than  one  ovum  per  100  fields. 

The  diagnosis  may  be  made  by  direct  examination  of  the  stool, 
but  concentration  methods  are  much  better  on  account  of  the 
scarcity  of  ova.  The  brine  method  of  Barbour  was  found  most 
useful  for  examination  of  large  numbers  of  men  during  the  war. 
The  feces  were  mixed  with  equal  parts  of  a  hypertonic  salt  solu- 
tion in  a  smaU  container  such  as  a  salt  cellar  or  pill  box  and  allowed 
to  stand  a  few  minutes.  The  eggs  float  to  the  top  and  will  attach 
themselves  to  the  imder  side  of  a  sHde  placed  over  the  surface. 

TREATMENT 

This  is  the  same  as  for  a  mild  infection.  Carriers  can  be  cured 
by  a  course  of  thymol,  oil  of  chenopodium  or  carbon  tetrachloride. 
If  possible,  the  stool  should  be  strained  and  worms  counted.  Sub- 
sequent examination  will  teU  results  of  treatment. 

In  general  management,  carriers  must  be  considered  in  same 
class  with  cases,  and  feces  should  be  disposed  of  so  that  soil  will  not 
be  infected.  As  the  cure  is  so  easy,  no  hardships  on  the  individual 
are  necessary. 

Smtllie,  W.  G.:  Am.  Jour.  Trop.  Med.,  1921,  i,  389. 


CHAPTER  IX 

Diphtheria 

It  is  generally  accepted  that  diphtheria  is  largely  kept  in  exist- 
ence by  chronic  carriers  who  act  as  reservoirs  and  furnish  the 
bacilli  at  favorable  seasons  to  susceptible  individuals.  If  it  were 
not  for  carriers  the  disease  would  be  much  less  of  a  problem.  On 
the  theoretical  side  the  control  of  carriers  has  been  carried  nearly 
to  a  stage  of  perfection.  The  possible  carrier  can  be  diagnosed 
with  comparative  ease.  The  virulence  of  the  suspected  organism 
can  be  determined  with  considerable  certainty.  The  susceptibil- 
ity of  possible  hosts  can  also  be  determined  and  the  treatment  of 
the  carrier  is  fairly  effective.  Hence,  theoretically  we  are  in  a 
very  favorable  position  to  stamp  out  this  disease  along  carrier 
lines.  Practically,  however,  the  program  usually  breaks  down 
because  it  is  too  big.  The  number  of  exposed  and  susceptible 
persons  is  usually  large.  The  laboratory  and  chnical  facilities  are 
usually  Hmited.  Only  a  certain  number  of  cultures  can  be  ex- 
amined in  a  day  and  only  a  much  smaller  number  of  virulence 
tests  can  be  made.  Only  a  certain  number  of  Schick  tests  can  be 
made  and  several  days'  observation  are  needed.  Only  a  certain 
number  of  persons  can  be  quarantined  or  held  under  observation. 
The  result  is  that  the  purely  bacteriological  line  of  attack  fails  and 
common  sense  governs  as  it  should.  Clinical  cases  are  considered 
first  and  as  much  carrier  work  is  done  as  is  feasible.  As  labora- 
tory facilities  increase,  more  is  accomplished  along  these  lines, 
but  it  is  doubtful  if  carrier  work  alone  can  be  sufficiently  well  done 
to  produce  a  radical  effect  on  the  prevalence  of  diphtheria.  The 
most  promising  results  are  being  obtained  by  a  combination  of 
case  work,  carrier  work  and  active  immunization  of  Schick  positive 
children.  The  toxin  antitoxin  treatment  seems  to  give  a  high  and 
lasting  immunity  and  the  most  practical  objective  is  to  produce 
a  large  number  of  immunes  along  with  a  reduction  of  the  foci  of 
infection.  The  immunization  program  is  not  sufficient  alone  as 
the  reactions  among  adults  are  too  severe  for  general  practice. 

72 


DIPHTHERIA  73 

However,  the  fear  of  producing  a  large  number  of  carriers  among 
immunized  children  is  groundless,  as  these  contact  carriers  are 
temporary.     The  worst  carriers  are  the  chronic  convalescent  ones. 

Incuhationary  carriers.  These  carriers  can  be  recognized  and 
play  some  part  in  the  dissemination  of  bacilli,  but  the  incubation 
period  is  so  short  and  the  diagnosis  of  a  virulent  organism  in  a 
Schick  positive  individual  requires  so  much  time  that  the  incuha- 
tionary carrier  cannot  be  assigned  a  very  definite  place  in  carrier 
work.  If  they  are  found,  however,  they  should  be  treated  like 
cases. 

Convalescent  carriers.  With  convalescence  the  bacilli  begin 
gradually  to  disappear  and,  by  the  end  of  a  month,  85  per  cent  of 
convalescents  are  bacteriological  recoveries.  By  the  end  of  a 
second  month,  98  per  cent  are  free.  The  remainder  pass  into  the 
most  dangerous  class  of  more  or  less  chronic  carriers.  Foreign 
bodies  or  deformities  in  the  nose  and  throat  predispose  to  the 
chronic  carrier  state.  Release  cultures  made  during  early  con- 
valescence are  examined  only  morphologically.  Virulence  tests 
are  not  necessary  as  it  has  been  found  (Wadsworth)  that  90  per 
cent  of  strains  from  convalescent  carriers  are  virulent  up  to  three 
months  after  recovery. 

Contact  carriers.  Pure  contact  carriers  occur  among  attendants, 
families  and  contacts  of  cases  and  carriers  in  from  10  to  20  per  cent 
of  instances.  The  organisms  are  virulent  in  80  per  cent  of  in- 
stances, and  the  carriers  are  dangerous,  but  the  condition  is  tem- 
porary unless  there  is  some  predisposing  deformity  of  a  chronic 
focus.     These  carriers  are  iimnune  or  Schick  negative. 

In  the  general  population  true  carriers  of  virulent  organisms 
are  less  than  1  in  1000.  Among  children,  however,  2  per  cent  are 
true  carriers.  Only  10  per  cent  of  non  contact  or  non  convalescent 
carriers  show  virulent  organisms. 

Possible  and  pseudo  carriers.  In  any  extensive  carrier  work  a 
number  of  individuals  will  be  found  who  are  carrying  organisms 
which  morphologically  resemble  true  virulent  diphtheria  baciUi. 
A  preliminary  tentative  diagnosis  must  be  made  pending  further 
examination.  Virulence  and  cultural  tests  show  that  many  of 
these  organisms  are  diphtheroids  or  non-virulent  diphtheria 
baciUi.     The  final  diagnosis  should  be  made  of  pseudo  carrier  and 


74  CARRIERS   IN   INFECTIOUS   DISEASES 

the  individual  should  be  released  from  observation.  No  long 
term  quarantine  should  be  carried  out,  as  has  been  done,  on 
morphological  grounds  alone. 

PATHOLOGY 

The  focus  in  incubationary  carriers  is  at  the  site  of  the  com- 
ing lesion,  usually  in  the  throat  near  the  tonsils  and  consists  in  the 
first  stages  of  invasion.  The  number  of  organisms  is  probably 
large. 

In  the  contact  carrier  there  is  either  no  lesion  or  a  nonspecific 
one  due  to  some  other  cause  such  as  a  foreign  body  or  a  deformity 
on  which  the  bacilli  become  engrafted.  The  lesion  then  comes 
to  resemble  that  of  a  convalescent  carrier. 

Chronic  convalescent  carriers.  The  tonsil  is  most  frequently  the 
focus  in  the  chronic  convalescent  carrier  and  may  be  taken  as 
typical.  Other  similar  foci  may  exist  in  the  adenoids  or  sinuses, 
but  the  tonsil  is  most  frequently  and  longest  infected.  The  crypts 
have  a  local  diphtheritic  inflammation  of  their  walls.  The  Hning 
epithelium  is  disintegrated  and  replaced  by  inflammatory  tissue 
which  pours  out  an  exudate  into  the  crypt  and  on  the  surface  of 
the  tonsil  (fig.  1).  There  is  a  characteristic  fibrinous  exudate  in 
the  lesion.  The  diphtheria  bacilH  are  easily  found  in  sections  and 
are  clearly  out  of  reach  of  surface  disinfection  (fig.  10).  These 
carriers  have  a  general  but  not  a  local  immunity.  The  general 
immunity  may  be  carried  over  from  the  disease  or  it  may  be  con- 
stantly produced  by  the  small  carrier  lesion  which  acts  as 
a  vaccination. 

DIAGNOSIS 

Suspected  diagnosis  may  be  made  on  epidemiological  or  clinical 
grounds,  and  a  clean  tonsillectomy  is  evidence  against  the  carrier 
state,  but  the  final  diagnosis  is  bacteriological  and  the  presumptive 
laboratory  diagnosis  is  relatively  so  simple  that  wholesale  cultures 
are  usually  made  without  regard  to  chnical  or  epidemiological 
probabilities.  If  Schick  tests  have  previously  been  made  on  any 
of  the  suspects,  the  results  should  be  obtained. 

The  specimen.  A  sterile  swab  should  be  pressed  on  each  tonsil 
and  passed  over  the  faucial  entrance.    Repeated  examinations  in- 


DIPHTHERIA 


75 


crease  the  percentage  of  positive  results.  Nasal  specimens  ob- 
tained by  passing  separate  swabs  through  each  side  of  the  nose  to 
the  nasopharynx,  also  reveal  additional  carriers.  Nasal  obstruc- 
tion ma}^  interfere  with  free  passage  of  the  swab,  but  may  be  the 


S    % 


Fig.  10.  Diphtheria  Bacilli  in  Tonsil  of  a  Convalescent  Carrier 

Three  Months  After  Attack.    Higher  Magnification  of 

Previous  Photograph  (Fig.  1).     X  1000 

Diphtheria  bacilli  in  the  walls  of  the  crypts.     Bacilli  cultivated  from 
this  tonsil  were  virulent  for  guinea  pig. 

predisposing  cause  of  the  infection.  The  swab  should  be  immedi- 
ately passed  over  the  surface  of  coagulated  blood  serum  in  a 
tube  or  box  or  plate  and  incubated,  or  the  swab  be  sent  to  the  labo- 
ratory and  inoculated  there.     The  organisms  resist  drying  and  low 


76  _  CARRIERS   IN    INP^ECTIOUS    DISEASES 

temperature,  but  speed  is  an  ol)ject.  Direct  smears  from  the 
throat  are  not  as  useful  in  the  diagnosis  of  carriers  as  they  are  in 
some  cases. 

While  the  .culture  is  incubating  Schick  tests  should  be  started, 
if  possible,  by  the  intracutaneous  injection  of  0.2  cc.  of  ^  m.l.d. 
of  toxin  for  a  guinea  pig  of  250  grams  with  a  control  of  toxin  heated 
to  75°  for  five  minutes. 

Usually  the  incubation  is  carried  on  for  over  night  but  shorter 
incubation  gives  positive  results  in  some  cases.  Incubation  for 
48  hours  is  said  to  increase  positive  results  by  about  10  per  cent. 
Smears  are  made  from  suspicious  colonies  or  from  the  mass  growth 
and  are  stained  by  alkaline  methylene  blue,  Gram's  or  Neisser's 
stain.  The  presumptive  diagnosis  is  made  on  morphological 
grounds.  No  special  morphology  of  carrier  strains  is  recognized. 
Doubtful  findings  should  be  checked  by  further  specimens  and 
more  detailed  examination.  Meanwhile  possible  carriers  should 
be  quarantined.  If  the  carrier  is  an  early  convalescent  or  contact 
carrier,  a  virulence  test  is  not  necessary  as  most  of  these  strains 
are  virulent.  But  if  the  carrier  state  is  long  continued  or  of  doubt- 
ful origin,  virulence  tests  must  be  made. 

TECHNIQUE 

It  is  of  course  most  satisfactory  to  isolate  the  organism  in  pure 
culture,  but  in  view  of  the  large  number  of  cultures  to  be  tested 
a  rough  test  may  be  more  serviceable.  The  slant  from  which  the 
diagnosis  was  made  is  washed  off  in  2  cc.  NaCL  and  1  cc.  injected 
subcutaneously  in  a  guinea  pig.  If  the  pig  does  not  die  in  three 
days  it  may  be  concluded  that  the  culture  is  avirulent.  If  the 
pig  dies  with  characteristic  injection  oedema  of  the  site  of  inocula- 
tion and  with  hyperaemia  of  the  adrenals  it  may  be  concluded  that 
the  culture  is  virulent.  Too  often,  however,  the  pig  dies  with 
indefinite  evidences  and  it  can  not  be  decided  whether  the  animal 
died  of  diphtheria  intoxication  or  mixed  infection. 

A  pure  culture  is  obtained  by  emulsifying  material  from  the 
original  tube  in  broth  and  spreading  a  loopful  well  over  a  blood 
agar  plate.  Loeffler  plates  may  be  used,  but  are  more  trouble- 
some to  make  and  are  not  much  superior.  Single  suspected  colonies 
are  fished  and  stained  and  if  positive  morphologically  are  trans- 


DIPHTHERIA  77 

ferred  to  broth  or  to  a  Loeffler  or  blood  agar  slant.  After  forty- 
eight  hours  1  cc.  of  the  broth  culture  of  a  virulent  organism  should 
kill  a  pig  in  three  days.  If  the  slant  is  used  it  is  washed  off  and 
one-half  is  given.  As  a  control,  a  guinea  pig  may  be  injected  with 
the  same  dose  and  immunized  with  500  units  of  antitoxin,  but 
ordinarily  this  is  not  necessary.  It  is  more  economical  to  use  the 
intracutaneous  method  by  which  a  number  of  tests  can  be  made 
on  the  same  animal,  but  more  experience  and  skill  are  necessary. 

When  a  carrier  is  found  an  attempt  should  be  made  by  regional 
cultures  to  locate  the  focus.  Usually  both  tonsils  are  infected  but 
the  infection  may  be  in  one  or  in  one  side  of  the  nose. 

There  are  now  several  possibilities.  The  patient  may  have  a 
virulent  organism  and  a  negative  Schick  test — he  is  a  true  carrier, 
contact  or  convalescent.  The  history  may  decide  which.  He 
ma}'  have  a  non-virulent  organism  and  a  negative  Schick  test; 
he  is  a  pseudo  carrier.  He  may  have  a  virulent  organism  and  a 
positive  Schick  test;  he  may  be  an  incubationary  carrier  or  early 
case  and  should  have  antitoxin.  He  may  have  an  avirulent  or- 
ganism and  a  positive  Schick  test,  he  is  a  psuedo  carrier,  but  toxin 
antitoxin  treatment  should  be  considered. 

As  was  said  before,  in  trjdng  to  handle  large  numbers  of  cases, 
as  in  schools  or  troops,  this  ideal  scheme  usually  breaks  down  and 
common  sense  rules,  that  is,  cases  are  given  priority  and  carriers 
are  considered  if  possible. 

TREATMENT 

Many  carriers  clear  up  by  themselves  in  time.  Release  cul- 
tures should  be  continued.  For  the  resistant  cases,  many  lines 
of  treatment  have  been  proposed,  but  excision  of  the  focus  by 
tonsillectomy  is  the  most  effective  except  in  the  rare  cases  when  the 
lesion  is  elsewhere.  On  the  specific  side,  antitoxin  does  not  affect 
the  bacteria.  An  antibacterial  serum  has  been  made  and  used  as 
powder  for  use  by  insufiiation.  Cures  have  been  reported,  but 
cures  have  also  followed  the  use  of  powdered  meningococcus 
serum.  The  effect  is  probably  a  non-specific  inflammatory  reac- 
tion. Insufflation  of  kaoHn  also  acts  in  the  same  way.  Attempts 
have  been  made  to  implant  lactic  acid  baciUi  and  staphylococci. 
The  former  is  ineffective,  the  latter  dangerous.     Every  sort  of 


78  CARRIERS   IN   INFECTIOUS   DISEASES 

antiseptic  has  been  proposed.  The  most  reasonable  are  silver 
nitrate,  10  per  cent,  and  iodine,  2  per  cent  in  glycerin.  If  these 
antiseptics  are  applied  actually  to  crypts  they  may  succeed  in 
some  cases;  but  this  procedure  requires  more  care  than  is  usually 
available  and  the  crypts  have  underground  communications.  It 
is  simpler  and  more  effective  to  remove  the  tonsil.  This  operation 
however,  should  not  be  done  until  several  months  after  the  disease 
in  order  to  avoid  the  complication  of  endocarditis. 

X-ray  treatment  of  the  tonsil  has  been  proposed  and  is  prefer- 
able in  some  cases.  Several  treatments  are  necessary.  The 
action  is  to  shrink  up  the  lymphatic  tissue  and  improve  nutrition 
and  drainage.     There  is  no  antiseptic  effect. 

In  cases  which  resist  tonsillectomy,  correction  of  other  foci 
possibly  in  sinuses  and  irrigation  of  nose  and  throat  with  saline  is 
indicated. 

Isolation.  Carriers  of  virulent  bacilli  should  be  isolated. 
Appropriate  treatment  for  the  kind  of  carrier  should  be  carried  out. 
For  release,  three  successive  negative  cultures  should  be  required 
at  daily  intervals  without  any  local  treatment.  No  protracted 
isolation  should  be  imposed  unless  the  organisms  are  proved  to  be 
virulent. 

Wadsworth,  a.  B.:  Jour.  Amer.  Med.  Assoc,  1920,  xlvii,  1633. 
Weaver,  G.  H.:  Jour.  Amer.  Med.  Assoc,  1921,  Ixxvi,  831. 
Spooner,  L.  H.:  Jour.  Amer.  Med.  Assoc,  1920,  Ixxiv,  582. 
Keefer,  F.  R.,  Friedburg,  S.  A.,  and  Aronson,  J.  D.:  Jour.  Amer.  Med. 
Assoc,  1918,  1206. 


CHAPTER  X 

Epidemic  Meningitis  (Meningococcus  Infection) 

Next  to  diphtheria  carriers,  carriers  in  meningitis  have  the  most 
definite  place  among  the  respiratory  diseases.  The  experiences  of 
the  war  brought  the  carrier  aspects  of  the  disease  especially  into 
prominence.  It  is  probably  more  exact  to  speak  of  meningococcus 
infections  than  of  meningitis,  because  apparently  there  may  be  a 
local  infection  in  the  nasopharynx  and  a  blood  infection  without 
true  meningitis.  The  carrier  is  recognized  as  an  essential  part  in 
the  continued  existence  of  the  disease.  The  case  is  generally 
too  sick  to  spread  the  germs  extensively,  while  the  carrier  is  free 
to  do  so.  On  the  other  hand,  the  radical  control  of  the  disease  by 
carrier  work  alone  is  generally  considered  impossible  on  account 
of  technical  and  administrative  difficulties.  Our  insufficient 
knowledge  of  virulence  and  immunity  also  weakens  a  radical 
carrier  attack.  Enghsh  experience  has  also  apparently  shown 
that  increasing  the  air  space  is  usually  effective  in  controUing  the 
disease  among  troops.  Carrier  work,  therefore,  tends  to  be 
confined  to  convalescents  and  immediate  contacts  and  is  com- 
bined with  other  general  measures. 

The  object  of  the  carrier  program  is  of  course  to  prevent  a 
virulent  organism  from  reaching  a  susceptible  individual.  In  the 
problem  of  the  meningococcus  infection,  we  have  no  simple  clinical 
method  of  determining  either  the  virulence  of  the  meningococcus 
or  the  susceptibility  of  the  host.  Such  bacteriological  and  clinical 
work  as  has  been  done  on  the  subject  indicate  the  following  situa- 
tion (Heist).  Strains  from  the  throats  of  carriers  are  not  as  viru- 
lent as  strains  from  the  spinal  fluid  of  cases.  Some  carrier  strains 
are  more  virulent  than  others.  Not  over  5  per  cent  of  persons  are 
susceptible  to  carrier  strains.  The  results  seem  to  throw  some 
light  on  the  epidemiology  of  meningitis  and  may  explain  the  dif- 
ference between  the  seriousness  of  the  case  and  the  relative  harm- 
lessness  of  the  carrier. 

Incubationary  carriers  exist  and  constitute  about  0.5  per  cent 
of  all  carriers.     Convalescent  carriers  number  up  to  5  per  cent  for 

79 


80  CARRIERS   IN   INFECTIOUS   DISEASES 

three  months  after  convalescence  and  occasionally  much  longer. 
Contact  carriers  are  more  temporary,  but  more  numerous.  Some 
surveys  made  during  the  war  ran  very  high  with  but  very  few  cases. 
In  the  general  population  the  percentage  is  about  3.  As  we  have 
no  simple  test  for  virulence  and  immunity,  the  only  logical  carrier 
method  of  attack  would  be  to  examine  all  concerned  and  to  isolate 
those  carrying  either  of  the  two  recognized  types  of  meningococci. 
The  amount  of  technical  and  administrative  work  involved  usually 
defeats  such  a  plan. 

Special  mention  should  be  made  of  one  feat  during  the  war  in 
which  the  entire  89th  Division  of  40,000  men  were  cultured  for 
carriers.  Tliis  was  done  under  the  direction  of  Lieutenant- 
Colonel  E.  H.  Schorer  at  Camp  Funston,  Kansas.  The  Division 
Surgeon  was  Colonel  J.  L.  Shepard,  M.C.,  U.  S.  A.  The  men  came 
from  an  endemic  area  of  meningitis  and  in  spite  of  the  ordinary 
measures,  cases  continued  to  appear.  It  was  decided  to  examine  the 
entire  division  for  carriers  and  this  was  accomplished  in  about  six 
weeks,  by  using  six  officers  as  swabbers  and  nine  officers  in  the 
laboratory  while  the  enhsted  men  worked  in  day  and  night  shifts. 
About  3  per  cent  of  carriers  were  found.  Altogether  during  the 
winter  of  1917-1918,  102,170  cultures  were  made  and  3290  carriers 
were  detected  and  removed  from  their  organizations.  Meningitis 
ceased  to  be  a  problem  when  the  work  was  accomphshed.  The 
results  have  been  criticized  on  the  ground  that  such  mass  work  is  too 
crude  technically.  Some  evidence  on  this  point  is  seen  in  the  fact 
that  out  of  a  total  of  152  cases  of  meningitis,  16,  or  over  10  per  cent 
occurred  in  incubationary  carriers  who  had  been  already  detected 
by  the  survey.  The  removal  of  these  men  alone  diminished  the 
exposure  rate  by  17  per  cent. 

At  the  outbreak  of  the  war,  the  expert  advisors  recommended 
general  carrier  work.  When  the  technical  difficulties  of  applying 
these  measures  on  a  large  scale  were  realized,  carrier  work  became 
limited  to  convalescents  and  immediate  contacts.  But  the  work 
at  Funston  showed  that  success  in  phorology  depends  largely  on 
the  energy  and  detennination  of  the  individuals  concerned  rather 
than  on  the  official  program.  If  the  laboratory  facilities  are  or  can 
be  made  adequate  and  if  the  circumstances  are  sufficiently  urgent, 
carrier  work  should  be  more  and  more  extensive. 


EPIDEMIC    MENINGITIS  81 


PATHOLOGY 


Comparative  regional  cultures  show  that  the  principal  carrier 
focus  is  in  the  vault  of  the  nasopharynx.  No  conclusive  patholog- 
ical studies  of  the  lesion  are  available.  It  is  usually  believed  that 
the  meningococci  hve  superficially  in  the  crypts  of  the  mucous 
glands.  A  large  amount  of  mucus  is  thought  by  many  observers 
to  indicate  the  carrier  possibihty .  But  in  some  instances  the  menin- 
gococci inhabit  the  epithehal  barrier  without  marked  disturbance. 
Predisposing  conditions  are  found  in  other  lesions,  especially 
deformities  of  the  nose  and  lymphoid  overgrowths.  Some  car- 
riers show  meningismus  with  a  normal  spinal  fluid. 

DIAGNOSIS 

The  diagnosis  can  sometimes  be  suspected  on  clinical  and  epi- 
demiological grounds  from  the  personal  history  and  evidence  of 
nasopharyngeal  trouble.  Skin  tests  with  bacterial  powder  or 
solutions  have  not  been  specific  enough  to  pick  out  carriers.  The 
agglutination  test  is  occasionally  valuable. 

The  bacteriological  diagnosis  requires  special  care  in  securing 
and  handhng  of  the  specimen,  as  the  organisms  lie  in  a  protected 
position  and  are  especially  fragile. 

A  good  nasal  swab  is  suflEicient,  the  more  elaborate  West  swab 
being  unnecessary.  The  most  open  side  of  the  nose  should  be 
entered  and  the  swab  pushed  to  the  back  wall  of  the  nasopharynx, 
then  rotated  and  withdrawn. 

The  specimen  should  be  kept  warm  and  moist  until  the  media 
is  inoculated.  The  media  must  also  be  kept  warm  after  inocula- 
tion. The  English  in  the  war  devised  special  warm  containers  to 
carry  specimens  in.  Whole  or  laked  blood  media  is  most  con- 
venient, but  any  serum  enriched  medium  can  be  used.  The 
specimen  is  planted  first  on  a  small  surface  at  the  edge  of  the 
plate,  then  with  a  sterile  loop  the  plate  is  streaked  radially. 
Schorer  put  several  cultures  on  the  same  plate.  After  incubation, 
typical  colonies  are  picked  and  stained  and  Gram  negative  cocci 
are  selected  for  further  work.  They  are  transferred  to  other 
media  for  macro-agglutination  or  in  some  instances  may  be  ag- 
glutinated microscopically  with  polyvalent  and  normal  and  para 


82  CARRIERS   IN   INFECTIOUS   DISEASES 

type  sera.    No  diagnosis  of  a  true  carrier  should  be  made  except 
with  type  identification. 

The  following  extracts  are  made  from  the  Standard  Technique 
of  Meningococcus  Carrier  Detection  issued  by  the  Medical  De- 
partments of  the  Army,  Navy  and  Public  Health  Services  during 
the  War:  These  directions  were  prepared  by  a  committee  of 
specialists  whose  chairman  was  Col.  F.  F.  Russell,  in  charge  of 
the  Division  of  Infectious  Diseases  and  Laboratories  of  the  Surgeon- 
General's  Office,  U.  S.  Army. 

I.    CULTURING. 

a.  Wherever  possible  the  cultures  should  be  taken  in  a  small 

room  in  the  regimental  infirmary.  The  floor  of  this  room 
should  be  washed  with  an  abundance  of  soap  and  water 
one  hour  before  the  men  enter  for  culture,  and  should  be 
wet  during  the  process  of  culturing. 

b.  Only  a  few  men  at  a  time  should  be  admitted  to  the    culture 

room. 

c.  Windows  and  doors  should  be  closed  all  the  time. 

d.  Cultures  should  not  be  made  within  an  hour  after  meals. 

e.  No  men  should  be  examined  on  the  same  day  on  which  they 

are  sprayed. 
II.  Method  of  Swabbing. 

a.  The  swab  used  should  be : 

1.  A  naked  wire  25  cm.  long,  with  a  small  absorbent  cotton 

pledget  on  one  end,  well  covering  the  end  of  the  wire, 
and  a  ring  handle  on  the  other.  The  wire  should  be 
flexible,  such  as  stove  pipe  wire  or  hay  baling  wire, 
of  about  18  gauge.  The  swabs  may  be  sterilized  in 
glass  or  paper  containers  in  groups  of  5-20.  The  last 
1  to  2  cm.  of  the  pledget  end  of  the  swab  is  bent  to  an 
angle  of  about  30  to  40  degrees.  This  swab  is  simple 
and  has  proved  most  satisfactory,  and  can  be  at  once 
discarded. 

2.  West   Tube.    This    gives    satisfactory    cultures,    but    is 

cumbersome,  and  not  strictly  necessary. 

3.  Straight  unprotected  nasal  swab.    This  is  useful  in  the 

case  of  individuals  with  highly  irritable  throats,  but 
is  not  recommended  as  a  routine. 

b.  The  subject  should  be  seated  facing  the  light.     Tongue  depres- 

sors are  to  be  used  when  necessary.  The  swab  should  be 
passed  behind  the  soft  palate  while  the  subject  is  phonat- 
ing.  The  swab,  having  passed  up  behind  the  palate,  is 
introduced  successively  into  each  posterior  naris,  and  then 
is  drawn  across  the  posterior  wall  of  the  naso-pharynx. 


EPIDEMIC   MENINGITIS  83 

The  swab  is  then  withdrawn,  taking  care  not  to  touch  the 
throat  surfaces  or  the  tongue;  this  is  best  accomplished 
during  phonation.  The  success  of  carrier  search  depends 
largely  on  the  care  with  which  the  swabbing  is  done,  hence 
the  man  taking  the  cultures  should  be  able  to  execute  these 
directions  skilfully.  He  should  be  either  a  nose  and 
throat  specialist,  the  bacteriologist  himself,  or  directly 
under  the  latter's  supervision. 
HI.  Method  of  Inoculating  Plates. 

a.  The  mucous  charged  swab  should  be  applied  over  a  limited  area 

at  the  periphery  of  the  plate.  From  this  the  spread  is 
made  by  a  wire  loop  passed  by  a  series  of  radial  strokes, 
each  starting  from  the  infected  point.  If  there  is  very 
little  mucus  it  is  often  possible  to  smear  directly  from  the 
end  of  the  swab. 

b.  A  single  person  per  10  cm.  plate  is  preferable.    More  than  two 

cultures  on  one  plate  should  never  be  made. 

c.  The  plate  must  be  inoculated  while  warm  and  kept  warm  until 

replaced  in  the  incubator.  To  accomplish  this,  sterile 
plates  already  warmed  by  storage  in  the  incubator,  should 
be  packed  in  a  device  insulated  against  the  loss  of  heat, 
such  as  a  fireless  cooker,  for  transportation. 
Care  should  be  taken  to  keep  the  plates  warm  during  the  inocu- 
lation process.  It  is  advisable  to  carry  a  plate  seeded 
with  known  culture  of  meningococcus  to  act  as  control. 
IV.  Culture  Medium. 

a.  Standard  nutrient  2  per  cent  agar.     (Beef  infusion,  or  Liebig's 

beef  extract,  0.5  per  cent  NaCl,  1  per  cent  peptone.  Fair- 
child's  or  Difco;  reaction;  plus  0.5,  phenolphthalein.) 
Dextrose  is  not  necessary.  A  convenient  method  of 
storage  is  in  200  to  300  cc.  quantities,  in  flasks  of  sufficient 
size  to  permit  of  the  addition  and  mixing  of  the  following : 

1.  Defibrinated  blood — human,  horse,  sheep,  goat,  or  rabbit 

— about  1  to  10  cc.  of  agar. 

2.  Laked  blood.     (Blood,  1  part;  distilled  water,  3  parts;  of 

this  mixture  add  1  to  10  cc.  of  agar.)  Both  these 
blood  preparations  should  be  stored  ready  for  use  in 
the  ice  box.  They  are  good  as  long  as  they  remain 
uncontaminated,  and  the  whole  blood  unhaemolysed. 
They  should  be  added  to  the  agar  only  when  the 
latter  is  at  a  temperature  of  45°  to  50°C. 

b.  Starch  agar  is  suitable  for  stock  cultures,  and  for  mailing 

cultures. 

c.  Plates  should  be  incubated,  inverted,  over  night  before  use, 

to  insure  sterility. 


84  CARRIERS   IN   INFECTIOUS   DISEASES 

V.  Examination  of  Inoculated  Plates. 

a.  Plates  should  be  inverted  when  placed  in  the  incubator, 

b.  Plates  will  be  ready  for  examination  after  twelve  to  eighteen 

hours'  incubation  at  37.5°C. 
0.  Discard  all  plates  that  are  crowded  and  do  not  show  discreet 

well  separated  colonies, 
d.  The  meningococcus  colony  on  the  whole  blood  medium  does 
not  produce  green  coloration  or  haemolysis.  It  tends  to 
be  somewhat  larger  than  the  streptococcus  and  pneumo- 
coccus.  The  colonies  are  moist,  elevated,  outlines  are  ill 
defined,  and  on  moderately  opaque  blood  agar  have  a 
faintly  bluish  tint.  The  colonies  are  not  usually  opaque, 
a  characteristic  which  distinguishes  them  from  the  staphy- 
lococcus. 
On  transparent  blood  medium  and  with  transmitted  light  under 
lens  magnification  the  colony  may  be  nearly  clear,  but  often 
shows  a  very  faint  smoky  gray-blue  quality.  This  charac- 
teristic is  intensified  by  passing  the  finger  between  the 
light  and  the  colony  to  shade  it.  Further  lens  effect  may 
be  seen  by  moving  the  plate  so  that  the  colony  passes 
across  some  distant  obstruction  to  the  light  as  a  string 
stretched  across  the  window.  The  colony  is  never  granu- 
lar, in  young  cultures. 
The  colony  should  be  confirmed  by  smear  and  Gram  stain. 
VI.  Transplantation. 

The  suspected  (ringed)  colonies  are  transferred  to  warmed  moist 
blood  agar  slants.  They  must  have  been  incubated  to  insure 
sterility.  It  is  best  to  keep  the  tubes  continuously  in  a  warm 
water  bath  until  finally  placed  in  the  incubator.  If  transfers 
are  made  under  these  conditions  there  will  be  enough  growth 
for  identification  in  about  eight  hours. 
Two  essentials  to  success  in  growing  meningococci  are  moist 
media,  kept  constantly  from  the  time  of  inoculation  at  body 
temperature. 
VII.  Identification. 

a.  Microscopic.     Smear    preparations    are    made    in    the    usual 

way  stained  by  Gram.  The  presence  of  a  few  gram  posi- 
tive, or  other  contaminating  organisms  does  not  make  the 
culture  unsuitable  for   agglutination. 

b.  Agglutination.     All  Gram  negative  micrococci   are  subjected 

to  agglutination  in  the  following  way: 
The  serum  dilutions  are  first  set  up,  and  the  bacterial  emulsion 
is  made  directly  in  them.  To  make  this  emulsion  a  loop- 
ful  of  the  suspected  culture  is  scraped  off,  and  the  loaded 
wire  is  passed  well  down  the  tube  almost  to  the  level  of  the 
fluid.     The  bacterial  mass  is  then  rubbed  off  against  the 


EPIDEMIC    MENINGITIS  85 

wall  of  the  tube  and  mixed  with  the  fluid.    In  the  case  of 
the  meningococcus  a  smooth  emulsion  is  usually  rapidly- 
produced.    Many  of  the  other  organisms  are  much  less 
readily  emulsified. 
An  emulsion  must  be  free  of  clumps  for  proper  agglutination 

tests. 
The  quantity  in  each  tube  should  be  1  cc.    The  tubes  are  then 
incubated  at  55°  for  twelve  to  eighteen  hours,  with  neces- 
sary precautions  against  evaporation. 
Controls.     Each  culture  should  be  run  in  parallel  with  a  normal 
horse   serum   control   at   1:50.     A  known  meningococcus 
culture  should  be  run  at  a  positive  control  with  each  set. 
VIII.  Reading  of  Agglutinations. 

The  tubes  which  have  been  clarified  are  then    shaken    gently 
when  the  clumps  can  be  clearly  detected  by  the  naked  eye  or 
hand  lens. 
The  organisms  which  are  agglutinated  by  the  polyvalent  serum 

dilutions  at  1:100  are  to  be  regarded  as  meningococci. 
Organisms  which   agglutinate   in   both   polyvalent   and   normal 

horse  sera  are  to  be  thrown  out. 
A  slight  opalescence  in  the  supernatant  fluid  due  to  contaminating 
organisms,  if  there  is  otherwise  distinct  evidence  of  alggutina- 
tion,  need  not  lead  to  the  discard  of  the  culture  as  negative. 
IX.  Typing. 

The  meningococcus  isolated  by  agglutination  with  polyvalent 
serum  should  be  typed  as  soon  as  possible.  If  this  procedure 
cannot  be  carried  out  on  the  spot,  the  cultures,  or  heated 
suspensions  of  the  cultures  in  saline  with  0.5  per  cent  phenol, 
should  be  sent  to  the  nearest  Department  Laboratory. 
XI.  Typing  of  Organisms. 

Organisms  recovered  from  spinal  fluid  or  blood  should  be  typed 
and  compared  with  the  organism  isolated  from  the  patient's 
nasopharynx. 
Inagglutinate  strains  are  sometimes  encountered.  To  establish 
further  the  nature  of  these  organisms  they  should  be  grown 
on  dextrose,  maltose,  and  saccharose  serum-litmus-agar. 
XII.  Indications  for  Culturing. 

On  the  appearance  of  a  case  of  cerebro-spinal  fever,  all  contacts 
should  be  cultured  for  the  detection  of  carriers  as  soon  as 
possible.  By  contact  is  meant  those  intimately  associated 
with  the  patient — that  is,  all  those  in  the  same  tent  or  squad 
room  with  him,  as  well  as  his  close  associates  at  mess  or 
elsewhere. 
Experience  has  shown  the  inadvisability  of  attempting  to  culture 
larger  groups  than  this. 


86  CARRIERS   IN   INFECTIOUS   DISEASES 

In  military  service,  those  who  give  positive  cultures  should  be 
held  in  the  detention  camp  until  they  have  had  three  succes- 
sive negative  cultures  at  five-day  intervals.  If  a  second  case 
appears  in  the  same  company  within  a  week  of  the  first  case, 
the  whole  organization  should  be  swabbed. 
XIII.  Disposal  of  Carriers. 

The  ordinary  carrier  usually  clears  up  in  a  week  or  two. 

Those  who  carry  longer  than  this  constitute  the  chronic  carriers, 
and  usually  give  large  numbers  of  colonies  or  even  pure 
cultures;  these  are  probably  the  important  cases  from  a 
public  health  point  of  view. 

Such  carriers  should  not  be  recommended  for  furlough  to  their 
homes,  nor  discharged  from  the  service  without  authority 
from  the  Surgeon  General. 

TREATMENT 

Fortunately  most  carriers  are  temporary  and  the  problem  is 
relatively  easy.  They  should  be  isolated  and  given  the  best  of 
hygiene,  especially  out-of-door  life.  Correction  of  deformities 
including  tonsillectomy  may  be  necessary. 

Many  antiseptics  were  tried  during  the  war  without  definite 
success.     In  some  instances  the  condition  was  made  worse. 

Specific  measures,  vaccination  or  serum  treatment,  have  no 
definite  place  in  treating  carriers. 

The  handling  of  carriers  in  large  numbers  requires  hospitahza- 
tion  and  quarantine.  The  plan  usually  collapses.  During  the 
war  carrier  camps  were  maintained  where  regular  work  was  done. 

Heist,  Solis-Cohen,  and  Solis-Cohbn:  Jour.  Immun.,  1922,  vii,  1. 
Medical  Research  Committee,  London,  Special  Eeport  Series,  Nos.  2,  3, 

17,  I  and  II. 
Blackfan,  K.  D.  :  Medicine,  1922,  i,  139. 
Nammack,  C.  H.  :  Med.  Record,  1919,  xcvi,  590. 


CHAPTER  XI 
Pneumococcus  Pneumonia 

Contrary  to  the  usual  historical  sequence,  carriers,  of  some  sort 
at  least,  were  discovered  before  cases  in  pneumococcus  pneumonia. 
Both  Sternberg  and  Pasteur,  in  1890,  demonstrated  the  presence 
of  pathogenic  micrococci  in  the  saliva  of  healthy  individuals 
before  the  possible  relation  of  these  organisms  to  pneumonia  was 
established.  Even  when  these  organisms  were  recognized  as 
pnemnococci,  there  was  little  or  no  advance  in  epidemiology  be- 
cause it  was  believed  that  pneumococci  were  homogeneous.  Only 
within  the  last  few  years,  since  the  recognition  of  types  of  pneu- 
mococci, has  come  the  possibility  of  intelligent  epidemiological 
and  carrier  work.  It  is  now  realized  that  the  true  carrier  is  a 
factor  which  cannot  be  disregarded. 

Before  the  differentiation  of  types,  it  was  taught  that  pneumo- 
coccus pneimionia  was  largely  autogenous  and  depended  on  a 
lowering  of  resistance.  It  is  still  true  that  this  kind  of  pneumonia 
occurs,  especially  following  influenza,  but  at  least  two-thirds  of 
the  cases  of  pure  lobar  pneumonia  are  caused,  not  by  the  Idnd  of 
pneumococcus  present  in  the  mouths  of  normal  persons,  Type  IV, 
but  by  Types  I  and  II.  These  are  the  epidemic  strains.  They 
are  not  found  ordinarily  in  the  mouth  except  in  convalescent  or 
contact  carriers. 

Type  IV,  or  more  exactly  Group  IV,  occurs  in  20  to  50  per  cent 
of  nonnal  mouths.  It  produces  about  one-fifth  of  the  total  num- 
ber of  cases,  especially  the  secondary  ones.  It  really  stands  for  a 
collection  of  types  which  cannot  be  recognized  and  handled  as  such. 
Hence,  Group  IV  carriers  do  not  figure  in  the  program.  Type  III 
and  atypical  Type  II  pneumococci  stand  between  Group  IV  and 
Type  I  and  Type  II  pneumococci.  They  are  definite  types  but  also 
occur  normally  in  the  mouth.  The  Type  I  and  Type  II  carriers  are 
the  only  ones  which  have  a  definite  place  in  carrier  work  at  present. 
The  subject  is  a  difficult  one  technically  and  the  recent  prevalence 
of  influenza  has  confused  the  situation  by  the  increase  of  other 

87 


88  CARRIERS   IN   INFECTIOUS   DISEASES 

kinds  of  pneumonia.  However,  there  is  no  doubt  that  the 
pneumococcus  Type  I  and  II  are  primary  causes  of  disease  (Cecil 
and  Blake)  and  that  the  carrier  relations  prevail.  In  view  of  the 
technical  difficulties  of  typing  and  of  our  known  lack  of  control, 
the  radical  handling  of  the  pneumonia  problem  by  the  carrier 
method  is  out  of  the  question.  Tests  of  virulence  and  suscepti- 
bility are  also  not  yet  available  as  practical  measures.  Something, 
however,  can  be  done  with  convalescent  carriers  and  immediate 
contact  type  carriers.  The  general  situation  must  be  handled 
by  general  hygienic  measures,  by  isolation  of  cases  and  carriers 
and  by  specific  vaccination. 

Convalescent  carriers  of  Type  I  and  II  pneumococcus  are  defi- 
nitely know^n,  as  about  40  per  cent  of  Type  I  and  II  convalescents 
have  the  type  organism  in  their  saliva.  These  are  usually  tem- 
porary, existing  about  a  month,  but  may  last  longer.  Contact 
carriers  are  also  well  recognized,  having  been  found  in  over  10 
per  cent  of  the  Rockefeller  Hospital  series.  They  are  also  tem- 
porary, lasting  about  a  month.  The  writer  made  a  study  of 
pneumonia  in  a  large  camp  in  1916  and  found  evidences  of  squad, 
company  and  regimental  type  epidemics.  Fifteen  per  cent  of 
tent  contacts  of  Type  I  cases  were  found  to  be  temporary,  contact 
carriers.     No  incubationary  carriers  were  detected. 

PATHOLOGY 

No  special  carrier  lesion  is  recognized  for  pneumococci.  As 
most  carriers  are  temporary  it  is  probable  that  no  special  lesion 
exists.  The  pneumococci,  apparently,  live  for  a  short  time  on 
the  mucous  membrane  of  the  mouth  like  the  more  saphrophytic 
types.  The  tonsil,  of  course,  is  a  favourable  soil,  but  type  carrier 
foci  have  not  been  definitely  located  there.  There  may  be  semi- 
chronic  lesions  in  the  lungs  or  bronchi,  but  they  have  not  been 
identified. 

DIAGNOSIS 

The  history  of  a  recent  attack  of  pneumonia  or  of  contact  with 
the  disease  raises  the  possibility,  but  the  type  of  the  previous  attack 
or  contact  is  often  unknown.  Bacteriological  diagnosis  must  be 
depended  on;  serological  reactions  are  not  definite  enough. 


PNEUMOCOCCUS   PNEUMONIA  89 

The  technique  is  more  difficult  than  in  a  case  as  the  organisms 
are  fewer  and  more  mixed  with  others.  A  faucial  swab  or  saHva 
can  be  plated  on  blood  agar  and  suspected  colonies  fished  to  glu- 
cose broth  for  tests,  but  it  is  better  to  use  the  mouse  method  by- 
injecting  0.5  cc.  of  mixed  saliva  into  the  peritoneum.  Sometimes 
the  peritoneal  exudate  can  be  used  directly  for  typing  as  in  cases, 
but  often  it  is  too  much  contaminated  and  cultures  of  heart  blood 
or  subcultures  of  peritoneal  exudate  must  be  made.  The  usual 
staining,  agglutination  and  bile  solubility  tests  must  be  made  and 
sometimes  be  supplemented  by  cultural  reactions.  Occasionally 
two  types  may  be  found,  as  I  and  IV.  Usually  only  one  saphro- 
phytic  type  is  present  in  the  mouth. 

TREATMENT 

Cases  should  be  isolated  as  far  as  possible  and  contact  should 
be  limited.  Convalescent  type  carriers  should  be  kept  isolated 
for  a  reasonable  time  or  until  two  or  three  negative  cultures  are 
obtained.  Contact  carriers  should  be  warned  of  possible  danger 
to  themselves  and  others.  They  should  be  kept  in  good  condition 
and  avoid  contaminating  others.  Usually  they  clear  up  in  a 
short  time.  On  analogy  the  nose  and  throat  should  be  looked 
after  for  local  predisposing  lesions.  No  data  are  available  on  the 
results  of  the  use  of  antiseptics. 

Laboratory  facilities  usually  are  too  limited  for  any  extensive 
general  carrier  work,  but  they  should  be  used  for  this  purpose  as 
far  as  possible. 

Avery,  O.  T.,  Chickering,  H.  T.,  Cole,  R.,  and  Dochez,  A.  R.M:  Mono- 
graphs of  the  Rockefeller  Institute,  No.  7,  1917.  Acute  Lobar 
Pneumonia.     Prevention  and  Serum  Treatment. 

Blake,  F.  G.,  and  Cecil,  R.  L.  :  Studies  on  Experimental  Pneumonia. 
Jour.  Exp.  Med.,  1920. 

Nichols,  H.  J.:  N.  Y.  Med.  Jour.,  1917,  August  4;  Met.  Surg.,  1917. 

Sailer,  Hall,  Wilson  and  McCoy:  Arch.  Int.  Med.,  1919,  xxiv,  600. 


CHAPTER  XII 

Streptococcus  Infections 

Historically,  the  best  known  carriers  of  streptococci  were  the 
surgeons  and  students  of  the  premicrobic  period,  who  after  treating 
cases  of  puerperal  fever  or  making  post  mortem  examinations, 
infected  puerperal  women  by  local  examination.  These  were 
mechanical  contact  carriers  who  do  not  belong  to  the  present  age. 

The  most  important  streptococcus  carriers  of  today  are  those 
involved  in  the  streptococcus  diseases  of  the  respiratory  tract, 
such  as  tonsillitis,  pharyngitis,  rhinitis,  sinusitis,  otitis  media, 
mastoiditis,  bronchitis,  pneumonia  and  empyema.  The  experi- 
ences of  the  war  and  of  the  influenza  pandemic  emphasized  the 
seriousness  of  this  group  of  diseases  and  much  work  has  been  done 
especially  on  the  carrier  relationships  of  streptococcus  hemolyticus. 
It  has  been  established  that  carriers  exist  and  play  a  part  in  the 
spread  of  the  organisms.  Methods  of  treatment  are  also  effective. 
The  part  played  by  carriers  in  the  production  of  the  disease  is  not 
so  clear.  The  principal  drawback  is  that  we  have  no  ready  means 
of  picking  out  true  carriers  from  among  possible  and  pseudo  car- 
riers. The  large  scale  on  which  any  measures  must  be  carried  out 
is  also  a  compUcation.  Finally  there  is  uncertainty  as  to  the 
primary  or  secondary  importance  of  the  streptococci.  Hence,  the 
role  of  carriers  is  still  obscure.  Radical  control  by  carrier  meas- 
ures is  not  possible  but  the  indications  are  to  push  the  carrier 
program  as  far  as  conditions  permit. 

There  are  of  course  other  streptococci  than  the  hemolytic  types 
in  the  respiratory  tract  and  in  some  cases  the  differentiation  of 
feeble  hemolyzers  is  not  simple.  Among  individuals  infected 
with  these  other  streptococci,  possible  carriers  exist.  If  the  cur- 
rent views  of  the  etiology  of  endocarditis  and  other  forms  of  focal 
infection  are  correct,  undoubtedly  some  virulent  strains  of  strep- 
tococcus viridans  are  carried  by  certain  individuals.  At  present, 
however,  these  true  carriers  cannot  be  picked  out  and  attention 
must  be  confined  to  carriers  of  hemolytic  streptococci. 

90 


STREPTOCOCCUS   INFECTIONS  91 

Some  workers  claim  that  by  repeated  cultures  hemolytic  strep- 
tococci can  be  found  in  100  per  cent  of  throats.  It  is  certainly 
true  that  a  single  culture  gives  no  adequate  picture  of  the  ultimate 
bacterial  flora  of  the  throat,  and  that  successive  cultures  increase 
the  percentage  of  positive  findings.  The  conclusion  should  not 
be  drawn,  however,  that  all  hemolytic  streptococci  found  in  the 
throat  are  normal  inhabitants.  All  the  evidence  points  to  the 
probabihty  that  there  are  different  groups  of  streptococci  and 
that  there  are  true  carriers.  During  the  war  surveys  showed  that 
recruits  freshly  arrived,  especially  from  rural  districts,  had  a 
relatively  small  percentage  of  positive  findings,  about  5  per  cent, 
which  soon  increased  to  equal  the  high  rates  of  those  who  had  been 
longer  in  crowded  camps,  50  to  80  per  cent.  These  surveys  were 
mostly  made  on  single  cultures  and  more  thorough  work  might 
have  raised  the  percentage,  but  could  hardly  have  obliterated  the 
striking  difference.  The  number  of  carriers  usually  detected  by 
ordinary  examination  is  10  to  20  per  cent. 

In  considering  the  question  of  groups  of  streptococci,  it  is 
fairly  well  settled  that  there  is  a  distinct  scarlet  fever  strepto- 
coccus. This  differentiation  has  been  made  on  immune  reactions 
and  confirmed  by  several  different  workers  and  is  so  clear  cut 
that  the  question  of  the  streptococcal  origin  of  scarlet  fever  is 
again  open.  The  further  grouping  of  hemolytic  streptococci  is 
not  so  definite.  Some  workers  (Dochez  and  Avery)  have  made 
four  groups  on  immunity  reactions,  while  another  worker  (Gordon) 
has  made  only  one.  The  sugar  reactions  in  all  the  groups  are 
generally  the  same  (Holman),  but  there  is  a  distinct  group  of 
mannite  fermenters  (streptococcus  infrequens).  Virulence  tests 
might  be  of  great  value  but  it  is  difficult  to  standardize  a  test  and 
virulence  falls  off  rapidly  on  subculture.  Havens  and  Taylor 
have  recently  done  some  work  in  this  line.  They  injected  into 
the  peritoneum  of  a  mouse,  one-fifth  of  a  twenty-four-hour 
growth  of  the  first  blood-agar-slant-transfer  from  the  original 
blood  agar  plate.  Death  in  twenty-four  hours  was  taken  as  the 
standard  of  virulence.  They  found  that  only  10  to  15  per  cent 
of  strains  from  carriers  were  virulent  while  of  strains  from  acute 
respiratory  cases  about  85  per  cent  were  virulent.  Virulence 
diminishes  rapidly  after  an  attack  of  tonsillitis,  for  example,  but, 


92  CARRIERS   IN   INFECTIOUS   DISEASES 

as  the  authors  point  out,  it  is  impossible  to  assume  that  these 
organisms  might  not  be  or  become  virulent  for  a  non-immune. 

Group  carriers.  The  only  way  to  approach  the  subject  is  to 
regard  carriers  of  streptococcus  pyogenes  and  streptococcus  in- 
frequens  (Holman)  as  possible  carriers.  Walker  and  Norton  have 
shown  that  the  infrequens  group  can  be  studied  as  a  unit  clinically 
and  epidemiologically.  As  virulence  and  susceptibihty  are  better 
understood,  it  will  be  possible  to  concentrate  on  the  true  carriers. 
The  carrier  is  probably  dangerous  to  himself  as  well  as  to  others. 
In  other  words,  relapsing  carriers  exist  who  suffer  clinically  when 
their  immunity  decreases. 

PATHOLOGY 

The  most  definite  carrier  lesion  is  found  in  the  tonsil.  Other 
foci  may  exist  in  the  adenoids,  turbinates  and  gums  but  the  tonsil 
is  the  richest  and  most  persistent  source  of  the  organisms.  The 
lesion  consists  of  an  actual  infection  of  the  crypt  wall.  The 
epithelial  lining  is  disintegrated  and  infiltrated  with  polynuclear 
leucocytes  (fig.  11).  Streptococci  are  also  found  in  the  crypt  con- 
tents, especially  in  the  actinomyces-like  granules  (Davis). 

The  typical  lesion  is  found  in  chronic  convalescent  carriers. 
Hypertrophied  tonsils  are  most  apt  to  be  positive.  Eighty  per 
cent  of  such  removed  tonsils  give  a  positive  culture.  In  contact 
carriers  the  streptococci  probably  also  lodge  in  the  tonsil.  It  is 
impossible  to  state  the  exact  pathogenesis  in  these  carriers.  The 
carrier  is  probably  temporarily  immune  to  his  own  organism,  but 
repeated  attacks  of  tonsillitis  are  of  course  the  rule. 

DIAGNOSIS 

The  presence  of  hypertrophied  tonsils  in  young  individuals  is 
suggestive.  Persons  with  clean  tonsillectomies  are  rarely  carriers 
or  if  so,  carry  few  organisms.  The  actual  diagnosis  is  bacterio- 
logical. The  specimen  should  consist  of  crypt  contents  and  is 
obtained  by  pressing  the  ordinary  throat  swab  on  the  tonsil  or 
going  into  the  crypts  with  a  loop.  Occasionally  the  lesion  is  uni- 
lateral. WeU  spread  smears  are  made  on  5  per  cent  blood  agar 
plates  and  after  twenty-four  hours  incubation,  hemolyzing  colonies 
are  examined  by  staining  for  Gram  positive  cocci  in  chains.     The 


STREPTOCOCCUS   INFECTIONS  93 

hemolytic  influenza  bacillus  and  hemolytic  staphylococcus  nuist 
be  ruled  out.  A  presumptive  diagnosis  can  often  be  made  on 
clear  cut  hemolysis  in  the  original  plate  and  speed  is  an  object 
when  cases  are  being  held  for  the  results  of  cultures.     Frequently 


Fig.  11.  Dkawixg  of  Sectiox  of  Tonsil  of  a  Streptococcus  haemolyticus 
Carrier.     X  1000 

Streptococci  are  shown  in  the  disintegrated  epithelial  covering 

the  hemolysis  is  not  clear  cut.  The  colony  must  be  subcultured 
into  broth  and  a  hemolysis  test  made  with  0.5  cc.  of  twenty-four 
hour  broth  culture  and  0.5  cc.  of  a  5  per  cent  suspension  of  red 
cells.  Even  with  this  test  some  results  are  partial  and  doubtful. 
Such  organisms  are  usually  regarded  as  non-hemolytic.     Further 


94  CARRIERS    IN    INFECTIOUS    DISEASES 

subdivision  is  made  by  sugar  reactions,  on  lactose,  mannite  and 
salicin.  Inulin  and  bile  solubility  tests  are  used  to  exclude 
pneumococci.  Immunological  classification  of  carrier  strains  is 
not  on  a  practical  basis.     Virulence  tests  are  also  not  standardized. 

TREATMENT 

As  in  diphtheria  carriers,  many  attempts  have  been  made  to 
cure  streptococcus  carriers  by  the  local  application  of  antiseptics. 
The  results  have  been  disappointing.  If  the  streptococci  were 
simply  growing  on  the  surface  of  the  crypt  walls  and  if  the  crypts 
were  all  accessible,  this  line  of  treatment  would  be  more  effective. 
But  the  streptococci  are  often  actually  in  the  wall  of  the  crypts 
and  the  crypts  have  underground  connections  which  cannot  be 
reached  except  by  dissection.  The  most  effective  antiseptic  in 
securing  negative  cultures  is  25  per  cent  silver  nitrate,  but  strepto- 
cocci can  still  be  cultivated  from  the  depths  of  the  crypts  after 
soaking  an  excised  tonsil  in  a  25  per  cent  silver  nitrate  solution. 

The  surest  method  of  treating  carriers  is  tonsillectomy.  Most 
cases  clear  up  immediately  after  the  operation.  In  some  instances 
a  few  streptococci  can  be  found  after  clean  tonsillectomies,  but 
the  danger  of  transmission  is  of  course  greatly  reduced  with  the 
number  of  organisms.  The  operation  should  not  be  done  until  a 
month  or  two  after  an  acute  attack,  in  order  to  avoid  systemic 
infection.  The  operation  must  also  be  a  complete  one  as  a  small 
tag  of  tissue  may  be  a  carrier  focus. 

X-ray  and  radium  treatment  have  been  proposed  as  a  substitute 
for  tonsillectomy  and  in  selected  cases,  in  which  there  is  a  con- 
traindication to  operation,  should  be  tried.  Undoubtedly  some 
tonsils  contract  considerably  under  this  treatment  and  the  num- 
ber of  organisms  become  smaller.  But  the  large  hypertrophied 
tonsils  are  less  suitable  than  the  boggy  ones  for  X-ray  treatment. 
Several  treatments  are  also  required  and  while  there  may  be 
clinical  improvement,  in  many  instances  the  streptococci  persist. 
This  result  is  of  course  a  failure  from  the  social  point  of  view. 

Probably  only  in  isolated  instances  will  an  operation  be  done 
simply  for  the  carrier  state.  This  state,  however,  is  an  additional 
argument  for  the  operation  when  coupled  with  clinical  indications. 


STREPTOCOCCUS   INFECTIONS  95 

The  following  recommendations  were  made  at  a  symposium  on 
this  subject  in  1919: 

I.  Our  knowledge  of  hemolytic  streptococcus  carriers  is  so  in- 
complete that  every  effort  should  be  made  to  answer  the  following 
questions : 

a.  Are  streptococci  found  in  carriers  all  of  equal  importance, 
or  are  there  different  groups  which  differ  in  chnical  significance? 

h.  Is  the  chronic  carrier  dangerous  to  himself? 

c.  Is  the  chronic  carrier  dangerous  to  others,  or  is  the  disease 
spread  chiefly  by  cases  or  by  case  contact  carriers? 

II.  In  the  absence  of  knowledge  on  these  points,  no  final  pro- 
gram for  handling  the  problem  can  be  stated,  but  a  tentative 
program  should  be  adopted  which  in  case  of  doubt  should  err  on 
the  safe  side. 

III.  When  no  streptococcus  disease  is  present  and  in  off  seasons. 

A.  For  soldiers  in  hospital.  Incoming  patients  with  throat 
infections  should  be  cultured  for  hemolytic  streptococci.  Any 
positive  case  with  diseased  tonsils  should  have  a  tonsillectomy. 
Clean  and  infected  measles  wards  should  be  maintained  for  prac- 
tice in  ward  technic. 

B.  For  soldiers  in  barracks.  Clinical  and  cultural  surveys 
should  be  made  for  the  detection  of  chronic  streptococcus  infec- 
tions such  as  tonsiUitis  and  otitis  media,  which  when  discovered 
should  be  treated  to  remove  possible  foci  of  future  epidemics. 

IV.  In  the  presence  of  streptococcus  compHcations  and  during 
the  streptococcus  season. 

A.  In  the  hospital. 

1.  No  carriers  among  attendants  should  be  allowed  in  surgical 
wards  or  in  wards  with  respiratory  diseases. 

2.  A  streptococcus  isolation  ward  should  be  established  to 
handle  special  cases. 

3.  Positive  and  negative  measles,  pneumonia  and  nose  and 
thi-oat  wards  should  be  maintained  with  strict  technic. 

4.  All  admissions  should  be  isolated  until  distributed  to  wards. 

5.  Throat  cultures  for  hemolytic  streptococci  should  be  made 
on  all  admissions  with  respiratory  diseases  for  record. 

B.  In  barracks. 

1.  Recruits  should  be  held  for  observation  and  cultured.  Posi- 
tive cases  should  be  separated  from  negative  as  far  as  possible. 


96  CARRIERS   IN   INFECTIOUS   DISEASES 

2.  Clinical  and  cultural  surveys  should  be  made  to  pick  out 
cases  of  tonsillitis,  otitis  media,  sore  throat  which  should  be  sent 
to  hospital. 

V.  In  the  absence  of  exact  knowledge  and  with  due  regard  to 
military  necessity,  no  attempt  to  isolate  all  streptococcus  carriers 
is  advocated  at  present. 

Havens,  L.  C,  and  Taylor,  M.  L.:  Am.  Jour.  Hyg.,  1921,  i,  192. 

Bryan,  J.  H.,  Nichols,  H.  J.,  Avery,  O.  T.,  Dochez,  A.  R.,  and  Lance- 
field,  R.  C,  Blake,  F.  G.,  and  Russell,  F.  F.  :  Symposium 
on  Streptococcus  Hemolj^ticus  Carriers.  Annals  of  Otology, 
Rhinology  &  Laryngology,  June,  1919. 

Methods  for  Isolation  and  Identification  of  Streptococcus  Hemolyticus 
adopted  by  the  Medical  Department  of  the  U.  S.  Army. 

Walker,  J.  E.:  Jour.  Exp.  Med.,  1920,  xxvii,  618. 

Sharp,  W.  B.,  Norton,  J.  F.,  and  Gordon,  J.  E.:  Jour.  Inf.  Dis.,  1922, 
XXX,  372. 

Kelbert,  Ellis:  Jour.  Med.  Res.,  1920,  xli,  387. 

Levy,  R.  L.,  and  Alexander,  H.  L. :  Jour.  Amer.  Med.  Assoc,  1918,  Ixx, 
1146. 

Nichols,  H.  J.,  and  Bryan,  J.  H. :  Jour.  Amer.  Med.  Assoc,  1918,  Ixxi, 
1813. 


CHAPTER  XIII 
Other  Respiratory  Infections 

By  analogy  the  carrier  aspects  of  the  large  group  of  diseases 
known  as  colds,  influenza,  etc.,  are  undoubtedly  important,  but 
little  practical  headway  can  be  made  along  carrier  lines  on  account 
of  the  uncertainty  as  to  the  etiology  of  these  diseases.  Many 
different  organisms  have  been  put  forward  as  causes,  but  none  is 
fully  accepted  as  a  primary  factor.  The  possibiHty  of  a  primary 
filterable  virus  must  be  disposed  of  before  any  advance  is  made. 
As  Metchnikoff  says,  this  possibility  is  a  "sort  of  ghost  preventing 
all  definite  conclusions  in  problems  connected  with  the  absence 
or  presence  of  microbes."  On  grounds  of  epidemiology  and  anal- 
ogy there  are  probably  incubationary  carriers,  convalescent 
carriers,  either  temporary  or  chronic,  and  contact  carriers.  But 
as  long  as  the  parasite  is  unknown,  nothing  can  be  done  along 
carrier  Hues  except  to  isolate  cases  early  and  continue  the  isolation 
for  a  reasonable  time.  There  is  no  better  illustration  in  medicine 
for  the  necessity  of  scientific  knowledge  as  a  basis  for  practical 
work.  Our  good  intentions  and  organizations  are  helpless  with- 
out it. 

INFLUENZA 

The  influenza  bacillus  is  the  principal  storm  center  in  this  dis- 
cussion. It  has  been  found  in  100  per  cent  of  cases  of  influenza 
by  combined  cultures  and  animal  inoculations.  It  has  also  been 
found  in  about  30  per  cent  of  convalescents.  On  the  other  hand, 
it  has  been  found  in  about  20  per  cent  of  normal  non-contact 
individuals.  The  value  of  any  set  of  statistics  can  not  be  deter- 
mined until  there  is  an  answer  to  the  following  questions:  Is  any 
form  of  the  influenza  bacillus  the  primary  cause  of  influenza? 
Are  there  groups  of  the  organism,  epidemic  and  saphrophytic? 
What  part  is  played  by  changes  in  virulence?  Until  we  have 
more  definite  knowledge  on  these  points,  no  practical  carrier  work 
can  be  done. 

97 


98  CARRIERS   IN   INFECTIOUS   DISEASES 

Irrespective  of  its  relationship  to  influenza,  the  influenza  bacillus 
is  recognized  as  a  pathogene,  especially  in  meningitis  in  children. 
There  is  some  evidence  of  the  existence  of  a  special  meningitis 
group  of  organisms  (Rivers).  The  hemolytic  influenza  bacillus 
is  usually  regarded  as  non-pathogenic. 

Pathology 

The  sinuses,  especially  the  sphenoids,  are  foci  for  the  influenza 
bacillus  (Hoplcins  and  Robertson).  At  autopsy  a  purulent  exu- 
date with  a  pure  culture  is  frequently  found.  The  working  out 
of  the  significance  of  the  lesions  depends  on  the  outcome  of  the 
work  on  the  problem  of  etiology. 

Diagnosis 

The  diagnosis  is  a  purely  bacteriological  one.  The  more  speci- 
mens from  different  parts  of  the  respiratory  tract  examined,  the 
higher  are  the  positive  results.  Usual  throat  swabs  are  inocu- 
lated on  chocolate  agar  and  colonies  made  up  of  Gram  negative 
bacilli  are  transferred  to  blood  agar  and  plain  agar.  The  results 
of  these  cultures  indicate  whether  the  organism  is  hemoglobino- 
philic  or  hemolytic.  Further  test  may  be  made  for  indol  produc- 
tion (Jordan)  which  separates  40  to  50  per  cent  of  influenza  bacilli 
from  Koch- Weeks  bacilli.  Toxicity  tests  and  grouping  at  pres- 
ent are  not  available. 

Treatment 

In  view  of  the  uncertainties  mentioned  above,  no  radical  carrier 
procedures  are  justified.  Cases  should  be  confined  to  bed  in 
isolation  for  a  reasonable  time. 

Vincent's  angina 

This  condition  shares  with  others  in  uncertainties  of  carrier 
work.  It  is  disabling  and  at  times  is  undoubtedly  epidemic. 
During  the  war  the  disease  was  quite  prevalent  in  the  form  of 
"trench  mouth."  In  attempting  to  handle  the  situation  along 
rational  lines  we  are  again  confronted  with  a  wilderness  of  con- 
fusion. The  organisms  of  Vincent's  angina  may  be  accepted  as 
causal  but  they  occur,  at  least  in  small  numbers,  in  normal  mouths 


OTHER   RESPIRATORY   INFECTIONS  99 

in  a  very  high  percentage  of  individuals.  They  are  practically 
nomial  inhabitants.  On  the  other  hand,  apparently  some  strains 
are  virulent  and  produce  ulcers  and  spread  to  others.  How  are 
the  two  organisms  related  to  each  other  and  to  the  disease?  Are 
they  primary  or  secondary  causes?  If  primary,  how  can  the 
epidemic  strains  be  identified?  There  is  no  adequate  answer  at 
present  to  these  crucial  questions.  Hence  no  scientific  basis 
exists  for  carrier  work. 

During  the  war  some  enthusiastic  medical  officers,  especially 
dental  officers,  tried  to  enforce  the  carrier  program  by  isolating 
all  cases  until  negative  release  examinations  were  obtained.  Con- 
tacts were  quarantined  on  the  mere  presence  of  a  few  fusiform 
bacilli  and  spirochetes  in  smears.  These  measures  threatened  to 
entirely  tie  up  the  activities  of  one  camp  and  were  ordered  dis- 
continued on  the  basis  that  our  knowledge  does  not  justify  such 
a  radical  program.  The  situation  must  be  handled  by  treatment, 
hygiene  and  sanitation  rather  than  carrier  work  at  present. 

TUBERCULOSIS 

The  term  carrier  is  sometimes  used  in  tuberculosis  to  indicate 
an  apparently  healthy  person  who  discharges  tubercle  bacilli. 
Such  true  convalescent  carriers  may  exist  who  have  a  general 
immunity  with  a  small  unhealed  lesion  somewhere  in  the  body. 
But,  in  general,  such  individuals  should  be  considered  as  mild  or 
chronic  cases.  In  view  of  the  nature  of  the  disease  and  of  its  mode 
of  spread,  more  good  will  be  done  to  the  individual  and  to  the 
group  by  emphasizing  cases  rather  than  carriers. 

On  the  other  hand,  if  the  term  is  accepted,  there  are  a  large 
number  of  true  relapsing  carriers.  As  infection  apparently  occurs 
in  childhood  and  clinical  cases  later  in  life  are  due  to  an  autogenous 
spread  from  a  chronic  glandular  focus,  we  may  say  that  relapsing 
carriers  are  of  the  greatest  importance  in  this  disease.  The  danger 
is  primarily  individual  and  secondarily  social.  One  organ  be- 
comes the  unit  and  the  individual  represents  a  group  of  organs. 
According  to  this  analysis,  the  relapsing  carrier  comes  under  the 
definition  of  a  carrier,  as  an  individual  who  harbors  and  transmits 
a  pathogenic  parasite,  only  as  the  parasite  is  transmitted  from 
one  organ  to  another.  This  extension  of  the  carrier  conception  is 
perhaps  undesirable;  but,  even  from  the  practical  point  of  view, 


100  CARRIERS   IN   INFECTIOUS   DISEASES 

a  consideration  of  the  importance,  pathology,  diagnosis  and 
treatment  of  relapsing  carriers  as  seen  in  latent  and  focal  infections 
is  instructive. 

DISEASES   OF   UNKNOWN   ETIOLOGY   OR   DUE   TO    FILTERABLE 
VIRUSES 

There  is  a  formidable  list  of  so-called  respiratory  diseases  in 
which  little  practical  carrier  work  can  be  done  as  the  cause  is 
unknown  or,  if  known,  requires  such  a  special  technique  for  identi- 
fication that  it  cannot  be  handled  chnically  or  in  a  public  health 
sense.  This  list  includes  measles,  scarlet  fever,  mumps,  smallpox, 
chicken  pox,  poliomyelitis,  encephalitis  and  possibly  influenza  and 
colds  (Foster). 

Work  on  poliomyelitis  has  been  most  instructive  in  this  group 
and  gives  a  rational  basis  for  at  least  some  carrier  measures.  The 
possibility  of  carrier  transmission  was  opened  up  by  epidemiolog- 
ical studies  before  experimental  confirmation  occurred.  After 
the  virus  was  identified,  it  has  been  shown  by  animal  inoculation 
(1)  that  incubationary  carriers  exist  (Taylor  and  Amoss);  (2)  that 
convalescent  carriers  exist,  occasionally  lasting  seven  months; 
(3)  that  contact  carriers  occur  which  probably  out-number  cases 
and  play  as  important  a  role  as  a  meningococcus  carrier;  (4)  that 
the  tonsils  are  foci  in  carriers. 

Considering  the  experimental  difficulties  involved  in  this  work, 
it  must  be  clear  that  even  the  few  observations  on  which  these 
statements  depend  have  thrown  much  light  on  the  problems  of 
prevention  of  this  disease  and  the  entire  group.  While  it  is 
usually  impossible  to  do  individual  carrier  work  at  present  on 
account  of  the  lack  of  laboratory  facihties,  some  general  rules  can 
be  laid  down.  Cases  should  be  isolated  at  the  earliest  possible 
moment.  Logically  the  same  rule  should  apply  to  any  indefinite 
sickness  in  chUdhood,  but  is  usually  out  of  the  question.  Conva- 
lescents should  also  be  isolated  for  about  three  weeks.  Contacts, 
if  they  occur,  should  be  under  suspicion.  The  tonsils  are  again 
shown  to  be  a  menace  and  the  hygiene  of  the  nose  and  throat  is 
emphasized. 

Vaughan,  V.  C:  Epidemiology  and  Public  Health.     1922,  vol.  I.     C.  A., 

Mosby  &  Company,  St.  Louis. 
Opie,   Blake,  Small  and  Rivers:  Epidemic  Respiratory  Disease.    1921, 

C.  V.  Mosby  and  Company,  St.  Louis. 


CHAPTER  XIV 
Blood  Diseases 

This  group  might  also  be  called  the  insect  transmission  group 
as  the  parasites  live  largely  in  the  blood  vessels  and  exit  is  usually 
provided  only  by  puncture  of  a  blood  vessel. 


Carriers  play  a  well  known  part  in  the  continued  existence  of 
malaria.  As  in  amoebiasis,  there  are  special  forms  of  the  parasite, 
called  gametes,  whose  function  it  is  to  perpetuate  the  life  of  the 
parasite  in  the  insect  host.  The  vegetative  forms  which  produce 
the  symptoms  are  not  infective  for  the  mosquito,  but  in  about 
50  per  cent  of  cases,  gametes  are  found  and  convalescent  or  re- 
lapsing carriers  result.  The  gametes  are  more  numerous  in  the 
chronic  than  in  the  acute  stages  of  the  infection.  Hence  all  the 
circumstances  are  favorable  for  the  infection  of  the  mosquito  by 
the  carrier. 

In  malarious  regions  gametes  are  found  in  the  blood  of  about 
10  per  cent  of  apparently  healthy  adults.  In  children  the  per- 
centage may  be  much  higher.  Strictly  speaking,  all  carriers  in 
malaria  belong  to  the  convalescent  carrier  group  either  as  chronic 
convalescent  or  relapsing  carriers.  An  infection  of  the  red  cells 
by  the  vegetative  forms  is  necessary  before  the  sexual  stages  can 
develop.  Hence,  the  true  contact  carrier  does  not  exist.  Prac- 
tically speaking,  however,  such  carriers  do  exist  in  the  sense  that 
they  have  never  been  conscious  of  their  original  infection. 

Pathology 

Carriers  in  malaria  are  particularly  instructive  from  the  point 
of  view  of  inununity.  There  is  a  true  infection  but  a  balanced 
parasitism  which  is  apparently  reached  by  an  antitoxic  without 
an  anti-parasitical  immunity.  A  special  focus  exists  in  the 
capillaries  of  the  spleen,  liver  and  brain.  The  balance  is  dehcate 
and  toxic  symptoms  or  frank  relapse  may  occur. 

101 


102  CARRIERS   IN   INFECTIOUS   DISEASES 

Diagnosis 

Previous  residence  in  malarial  regions  is  suggestive.  Clinical 
examination  may  show  an  enlargement  of  the  spleen.  In  the 
laboratory  examination  an  increase  of  mononuclear  leucocytes  is 
suggestive.  The  actual  finding  of  the  parasite  is  more  difficult 
than  in  cases,  as  the  parasites  are  fewer  and  the  gamete  must  be 
identified.  In  aestivo-autumnal  infections,  however,  the  gamete 
has  a  characteristic  crescent  shape  which  is  distinctive.  It  has 
been  estimated  (Darling)  that  a  certain  percentage  of  gametes 
per  mm.  of  blood  is  necessary  for  infection  of  the  mosquito  and, 
therefore,  to  constitute  a  carrier.  Usually  an  ordinary  blood  film 
is  made  and  stained  by  a  polychrome  method.  The  thick  film 
method  is  valuable  in  experienced  hands.  Cultural  methods 
(Bass)  are  difficult  technically  and  reveal  only  the  vegetative 
forms.  Various  drugs  have  been  suggested  to  bring  the  parasites 
into  the  peripheral  circulation  such  as  ergot  and  adrenalin.  Ultra 
violet  light  has  also  been  used  to  produce  relapses. 

Treatment 

The  prompt  treatment  of  an  acute  case  with  quinine  prevents 
the  development  of  gametes  and  hence  prevents  carriers.  After 
the  infection  is  estabHshed  the  treatment  of  carriers  must  be  more 
prolonged,  as  the  gametes  are  not  affected  by  quinine.  The 
formation  of  new  gametes  can  be  prevented  however,  and  the  old 
forms  gradually  disappear  from  the  blood.  Intravenous  therapy 
is  no  more  effective  than  aHmentary.  In  carriers  who  do  not 
tolerate  quinine,  arsphenamine  should  be  used. 

OTHER   DISEASES   OF   THE   BLOOD 

The  most  important  other  infectious  diseases  of  the  blood  are 
relapsing  fever,  yellow  fever,  trypanosomiasis,  filariasis,  bubonic 
plague  and  typhus.  Human  carriers  are  not  known  in  yeUow  fever, 
plague  or  typhus.  If  they  occur,  the  parasite  probably  leaves  the 
body  by  some  other  avenue  than  the  puncture  of  a  blood  vessel  by 
an  insect. 

Trypanosomiasis  is  so  progressive  and  fatal  a  disease  that  true 
carriers  do  not  occur  in  the  human  host.  In  the  animal  host, 
carriers  are  considered  in  a  later  section. 


BLOOD   DISEASES  103 

Filariasis  is  a  true  carrier  disease  in  the  sense  that  the  infected 
individual  often  shows  no  evidences  of  disease.  The  commonest 
variety  of  infection  is  due  to  Filaria  Bancrofti.  This  disease  is  of 
most  importance  among  native  races  in  the  tropics,  but  there  is 
a  focus  in  Charleston,  South  Carolina,  and  white  men  are  occa- 
sionally infected  in  the  tropics.  Probably  the  infection  occurs 
principally  in  early  life.  The  distribution  is  often  sharply  local- 
ized. Carriers  of  microfilaria  may  run  from  5  to  20  per  cent  in 
an  endemic  area  as  in  certain  islands  in  the  Philippines,  while 
in  other  islands  the  rate  is  much  lower. 

Pathology 

The  mother  worm  is  so  situated  in  the  lymphatics  that  no 
symptoms  arise.  Sometimes  there  are  internal  evidences  of 
disease  with  none  externally. 

Diagnosis 

Residence  in  an  endemic  area  is  suggestive.  Examination  of 
night  blood  shows  the  characteristic  periodicity  of  parasites  in  the 
peripheral  circulation.  The  parasite  can  also  be  found  by  exami- 
nation of  a  large  amount  of  day  blood. 

Treatment 

No  active  treatment  is  effective  at  present.  Carriers  should 
be  protected  from  mosquito  bites  to  prevent  spread.  They  can 
be  disregarded  otherwise. 

SKIN   DISEASES 

The  skin  is  of  course  infected  by  various  bacteria,  fungi,  blas- 
tomycetes,  spirochetes,  protozoa  and  metazoa  and  definite  carrier 
aspects  of  some  of  these  infections  occur.  It  is  not  considered 
worth  while,  however,  to  enlarge  on  this  subject  in  this  manual  at 
present.  The  lesions  are  usually  so  noticeable  and  so  accessible 
for  local  treatment  that  possible  carrier  lesions  are  usually  regarded 
as  mild  or  chronic  cases. 


CHAPTER  XV 

Sexual  Diseases 

1.  syphilis 

As  in  tuberculosis,  it  may  be  questioned  whether  it  is  correct 
to  speak  of  carriers  in  syphilis  rather  than  of  latent  cases.  The 
infection  is  so  apt  to  be  slowly  progressive  that  this  criticism  has 
some  point.  But,  unlike  tuberculosis,  sypliiHs  is  usually  spread 
by  a  form  of  contact  which  has  special  carrier  aspects.  It  also 
has  such  a  direct  although  insidious  effect  on  the  welfare  of  the 
race  that  an  exception  should  be  made,  if  necessary,  to  emphasize 
the  social  menace  of  the  situation.  The  prospective  bridegroom, 
infected  but  apparently  healthy,  is  really  carrying  spirochetes 
which  will  disable  his  wife  and  blight  his  offspring.  It  is  sphtting 
hairs  at  the  expense  of  pubhc  health  not  to  recognize  that  the 
apparently  well  syphilitic  is  a  great  danger  in  the  organized  social 
relations  of  marriage.  For  practical  purposes,  therefore,  cases  of 
latent  syphilitic  infection,  especially  males,  may  be  considered 
carriers.  They  have  all  the  characteristics  of  apparent  health 
combined  with  the  most  malign  possibilities  for  harm  that  other 
carriers  present.  The  female  infects  only  through  an  open  active 
lesion  or  occasionally  as  a  mechanical  carrier. 

The  number  of  latent  male  cases  is  somewhat  problematical  as 
it  depends  on  the  whole  number  of  cases  which  is  variously  esti- 
mated by  different  workers.  If  we  assume,  as  we  can  on  good 
grounds,  that  10  per  cent  of  adult  males  at  any  one  time  have 
syphiHs  and  that  50  per  cent  of  these  are  in  a  latent  stage,  then 
there  would  be  over  1,000,000  such  carriers  in  the  United  States 
at  present.  They  can  be  classed  as  chronic  convalescent  carriers 
as  they  have  recovered  from  the  acute  generalized  stage  of  the 
disease  and  have  reached  the  stage  of  locahzation,  or  they  can  be 
considered  as  relapsing  carriers. 

104 


SEXUAL   DISEASES  105 

Pathology 

The  carrier  lesion  is  in  the  testicle  in  the  great  majority  of  car- 
riers. There  are  many  other  foci  of  spirochetes  in  the  blood 
vessel  walls  of  other  organs  and  in  the  nervous  system,  but  these 
have  no  natural  outlet.  The  lesions  have  been  most  carefully 
studied  by  Warthin  by  the  combined  method  of  ordinary  histology 
and  of  sections  stained  for  the  organism.  They  consist  of  small, 
often  microscopic,  collections  of  lymphocytes  among  which  are 
nests  of  spirochetes.  In  the  testicles  these  foci  communicate  with 
the  tubules  and  the  organisms  are  discharged  with  the  semen. 

The  seriousness  of  the  situation  consists  in  the  fact  that  the 
spirochetes  are  genito tropic.  Experimental  work  has  shown  that 
the  testicles  are  the  most  favorable  place  for  their  growth  and  that 
they  lodge  there  by  preference.  Their  distribution  elsewhere  in 
the  body  may  be  determined  partly  by  chance,  but  they  will 
certainly  lodge  in  the  testicle  in  the  great  majority  of  cases. 
The  carrier  is  temporarily  immune  to  the  toxic  effects  of  the 
parasite,  but  not  locally  immune  to  the  parasite  itself.  A  balanced 
parasitism  is  reached  as  in  other  carriers. 

Diagnosis 

Illness  of  the  sexual  partner,  miscarriage  and  stillbirths  are 
suggestive.  A  truthful  personal  history  with  clinical  examination 
may  be  almost  conclusive,  as  the  presence  of  a  primary  scar  with 
adenopathy  and  the  history  of  previous  treatment  is  very  sus- 
picious. Very  often,  however,  the  carrier  is  truly  unaware  of  his 
condition.  The  original  attack  has  been  mild  and  unnoticed. 
For  exact  diagnosis,  a  confirmed  completely  positive  Wassermann 
reaction,  done  by  a  competent  serologist  and  in  the  absence  of 
certain  rare  diseases,  is  conclusive  evidence  of  syphilis.  This 
test,  taken  with  the  results  of  clinical  examination,  are  usually 
convincing.  Weak  reactions  and  indefinite  clinical  signs  of  course 
occur  and  make  it  necessary  to  balance  probabilities.  A  provoca- 
tive Wassermann  is  sometimes  valuable.  Examination  of  the 
spinal  fluid  is  justified  in  doubtful  cases  as  nervous  system  involve- 
ment is  probably  second  to  that  of  the  generative  organs. 


106  CARRIERS   IN   INFECTIOUS   DISEASES 

The  diagnosis  by  the  demonstration  of  the  spirochetes  in  the 
seminal  fluid  has  been  made  both  by  direct  examination  and  by 
animal  inoculation.  The  specimen  can  be  obtained  by  use  of  a 
condom  or  by  massage  of  seminal  vesicles.  Examination  by  the 
dark  field  microscope  or  by  injection  into  rabbits'  testicles  have 
given  positive  results  in  apparently  well  individuals  who  were 
candidates  for  marriage.  These  procedures,  however,  belong  more 
to  research  than  to  clinical  medicine.  The  virulence  of  the  para- 
site apparently  decreases  somewhat  as  the  disease  progresses,  but 
both  experimental  inoculation  and  chnical  experience  show  that 
the  virulence  remains  for  years  high  enough  to  infect. 

Treatment 

This  is  the  usual  one  for  the  disease' — the  chronic  combined 
treatment  with  arsphenamine  and  mercury.  In  general  the 
author  believes  that  optimism  as  to  results  is  justified.  Standards 
of  cure  are  not  entirely  agreed  upon;  but  a  carrier  should  not  be 
considered  safe  for  marriage  until  he  has  had  definite  treatment 
and  a  negative  serological  and  clinical  year  has  elapsed  with  no 
treatment.  Mechanical  protection  against  direct  contact  can  of 
course  be  used. 

2.  GONORRHOEA 

True  earners  exist  in  gonorrhoea,  both  in  males  and  in  females, 
and  are  responsible  for  a  good  share  of  the  trouble  caused  by  the 
gonococcus.  The  principal  bad  effects  are  blindness  in  children, 
sterility  and  chronic  ill  health  in  women,  stricture,  prostatitis  and 
arthritis  in  men.  The  line  between  a  chronic  case  and  a  carrier  can  be 
drawn  by  giving  sufficient  attention  to  liistory  and  examination. 
Most  carriers  are  of  the  convalescent  type.  The  percentage  of 
complete  cures  is  not  very  large.  The  pure  contact  carrier  may 
apparently  occur  in  the  prostitute.  She  may  be  a  primary  or 
secondary  contact  carrier  and  may  transmit  the  organisms 
mechanically  from  a  case  or  carrier  to  the  new  case. 

Pathology 

Small  inflammatory  or  ulcerative  lesions  persist  in  the  urethra, 
prostate,  seminal  vesicles  and  epididymus  or  in  the  cervix,  urethra 


SEXUAL   DISEASES  107 

and  Bartholin  glands.  They  are  usually  quiescent,  but  may 
become  active  after  sexual  intercourse,  alcohohsm  and  menstrua- 
tion. The  true  carrier  lesion  is  one  in  which  there  is  a  local  lesion 
but  a  general  immunity. 

Diagnosis 

Social  circumstances  and  history  may  suggest  the  examination. 
Local  examination  may  reveal  a  focus.  The  final  diagnosis  is 
either  bacteriological  or  serological,  but  in  either  case  difficulties 
may  be  met.  The  specimen  should  be  obtained  as  directly  from 
the  lesion  as  possible.  Definite  Gram  negative  intracellular  cocci 
in  discharge  from  the  genital  organs  is  practically  diagnostic.  In 
some  cases  the  organisms  can  be  isolated  by  cultures  and  confirmed 
by  cultural  and  serological  reactions.  Too  often  a  few  cocci  may 
be  found  extracellularly  which  cannot  be  isolated  in  pure  culture. 
The  unsatisfactory  nature  of  this  situation  was  recognized  by  the 
Inter-Departmental  Social  Hygiene  Board  and  work  along  these 
lines  was  encouraged.  A  precipitin  test  was  devised  which  con- 
sisted in  the  testing  of  an  autolyzed  exudate  against  a  known 
serum.  It  gives  clear  cut  results  at  times,  but  is  not  entirely 
specific.  The  complement  fixation  test  is  also  useful  if  positive, 
but  is  often  negative  in  known  carriers.  Altogether  the  detection 
of  the  carrier  is  not  very  satisfactory,  but  something  can  be  done. 
Regional  location  of  foci  is  necessary  after  the  organism  has  been 
found  or  serological  evidence  of  its  presence  has  been  obtained. 

Treatment 

The  usual  local  antiseptic  treatment  is  indicated.  New  mer- 
cury compounds  (Young)  have  more  than  ordinary  promise. 
Specific  treatment  is  uncertain  but  has  followers.  Non-specific 
treatment  also  has  its  advocates.  Local  treatment  after  identi- 
fication of  foci  is  most  helpful. 

Marriage  should  not  be  allowed  until  the  possibility  of  the 
carrier  state  has  been  ruled  out. 


108  CARRIERS   IN   INFECTIOUS  DISEASES 

3.    OTHER   VENEREAL   DISEASES 

Carriers  of  Ducrey  bacilli  are  not  definitely  known.  If  we 
admit  a  fourth  venereal  disease  in  the  fusospirillary  infection,  the 
carrier  relationships  of  this  infection  are  unknown,  but  probably 
resemble  those  in  Vincent's  angina. 

Vedder,  E.  B.  :  Syphilis  and  Public  Health,  1918,  Lea  and  Febiger,  Phila- 
delphia and  New  York. 

Nichols,  H.  J.:  Jour.  Amer.  Med.  Assoc,  1914,  Ixii,  1525;  Ixiii,  466. 

Young,  H.  H.,  White,  E.  C,  and  Swartz,  E,  O.  :  Jour.  Amer.  Med.  Assoc, 
1919,  Ixxiii,  1483. 


PART  III 
SUMMARY 


CHAPTER  XVI 

The  Relations  of  Phorology  to  Preventive  Medicine 

1.  the  place  of  carrier  work  in  preventive  medicine 

Preventive  medicine,  as  applied  to  the  infectious  diseases,  has 
a  many  sided  program  which  is  daily  producing  results.  This 
program  may  be  outlined  as  follows: 

A.  Prevention  of  the  spread  of  parasites  from  the  point  of 
multiplication  which  is  usually  in  the  host.  This  procedure 
involves  early  treatment  in  the  home  or  hospital,  the  disinfection 
of  infectious  discharges,  isolation  and  quarantine. 

B.  Prevention  of  the  spread  of  parasites  in  the  environment. 
This  is  one  of  the  aims  of  sanitation  and  includes  the  disinfection 
of  food,  drink,  air  and  the  destruction  of  insects. 

C.  The  personal  prevention  of  attacks  by  parasites,  or  personal 
hygiene.  This  field  includes  the  increase  of  personal  resistance 
and  the  avoidance  of  risks  of  infection. 

D.  Specific  immunity  by  vaccination  or  serum  prophylaxis. 
Any  one  of  these  measures  if  logically  and  completely  carried 

out  would  put  an  end  to  an  infectious  disease,  but  it  would  be  day 
dreaming  to  imagine  that  any  one  or  all  of  these  measures  can  be 
completely  carried  out  for  all  infections.  However,  by  suitable 
selection  of  means  for  ends,  many  soHd  results  are  being  obtained. 

Carriers  come  under  consideration  in  each  part  of  this  program. 

A.  The  measures  which  have  been  so  effective  against  case 
transmission  are  equally  eifective  against  carrier  transmission. 
Some  cure  themselves  under  quarantine  or  observation,  others 
can  be  cured  by  treatment.  The  relative  amount  of  attention 
which  should  be  paid  to  cases  and  carriers  from  this  point  of  view 
has  been  considered  under  each  disease.  The  program  of  course 
includes  the  diagnosis  of  carriers  and  this  is  one  of  the  limitations 
of  this  method  for  carriers  as  it  is  for  cases.  To  really  diagnose 
and  treat  every  case  and  carrier  of  an  infectious  disease,  especially 
during  an  epidemic,  would  require  an  organization  wliich  would 

111 


112  CARRIERS   IN   INFECTIOUS   DISEASES 

break  clown  of  its  own  weight.  There  would  have  to  be  a  labora- 
tory at  every  corner  and  an  inquisition  in  every  home.  A  medical 
officer  of  a  transport  once  estimated  that  if  ideal  ventilation  was 
provided  on  all  parts  of  the  boat,  all  the  power  would  be  used  up 
on  fans  and  the  boat  would  be  standing  still  in  the  middle  of  the 
ocean.  The  same  absurd  conclusion  would  be  reached  by  trying 
to  enforce  the  carrier  program  to  the  bitter  end.  As  was  evident 
during  the  war,  the  work  of  detecting  and  handling  carriers  was 
often  out  of  the  question  on  account  of  the  amount  of  work  and 
the  interference  with  the  aim.  Life  must  and  will  go  on  spite  of 
infections.  On  the  other  hand,  a  more  modest  attempt  is  often 
feasible  and  effective  on  a  small  scale.  While,  therefore,  this 
method  is  logically  and  practically  effective  within  limits,  it  alone 
cannot  be  counted  on  to  prevent  disease. 

B.  Granting  that  other  measures  are  necessary,  sanitation 
accomplishes  a  great  deal  and  must  be  directed  against  carriers 
as  well  as  against  cases.  The  relative  amount  of  protection  neces- 
sary against  carriers  cannot  be  accurately  Stated,  because  the 
dangers  are  unknown.  A  water  supply  must  be  unnecessarily 
chlorinated  for  many  days  of  the  year  in  order  to  be  safe  for  the 
whole  year.  Sanitation  undoubtedly  cuts  off  many  sources  of 
infection  from  carriers  in  water,  milk,  food  and  air.  The  limita- 
tions of  this  method  are  its  breakdown  at  critical  lines  due  to 
accident  or  human  weakness  and  to  its  failure  to  cover  contact 
infection.  We  have  at  present  no  means  of  sterilizing  respiratory 
droplets  in  the  air  of  street  cars  or  movies. 

C.  Personal  hygiene  has  advantages  and  hmitations  as  applied 
to  carriers.  It  usually  consists  of  two  parts,  the  m^aintenance  of 
resistance  and  personal  care  to  avoid  infection.  The  maintenance 
of  a  clean  nose  and  mouth  is  of  advantage  as  it  is  a  partial  pro- 
tection from  becoming  a  contact  carrier.  Care  in  personal  habits 
is  effective  against  carriers  as  against  cases.  There  are  limitations 
to  this  part  of  the  program,  however,  as  is  shown  in  the  recent 
development  of  "bacteriophobia."  Some  individuals,  including 
even  physicians,  have  become  so  particular  about  exposure  that 
they  have  lost  their  value  as  social  beings.  The  soldier  cannot 
think  of  personal  hygiene  as  applied  to  war  injuries.  There  are, 
however,  practical  and  reasonable  applications  which  are  of  value. 


PHOROLOGY   AND    PREVENTIVE   MEDICINE  113 

For  the  carrier  himself  personal  hygiene  means  preventing  the 
exposure  of  others  to  his  own  infection. 

The  following  is  a  summary  of  rules: 

a.  For  fgecal  and  urinary  carriers: 

(1)  Deposit  feces  and  urine  only  in  places  provided  for  such  a 
purpose  and  not  where  they  can  knowingly  infect  a  water  supply. 

(2)  Wash  hands  with  soap  and  water  after  going  to  the  toilet. 
Use  individual  paper  or  towel. 

(3)  Wash  hands  before  each  meal.  Use  individual  eating 
utensils. 

(4)  Do  not  engage  in  food  handling  occupation. 

(5)  Disinfect  soiled  underclothing  in  5  per  cent  carbolic  acid 
solution. 

(6)  Do  not  use  common  bath  tub;  use  sponge  or  shower  bath. 

(7)  Report  to  physician  for  periodic  examination. 
h.  For  the  respiratory  carrier 

(1)  Dispose  of  discharges  from  nose  and  throat  in  a  safe  way, 
in  spittoon  or  handkerchiefs.     Do  not  spit  promiscuously. 

(2)  Use  personal  eating  utensils. 

(3)  Wash  hands  when  soiled  with  respiratory  discharge.  Use 
individual  towel. 

(4)  Avoid  close  contact  in  talking;  avoid  kissing. 

(5)  Report  to  physician  for  treatment  and  regular  examinations. 

c.  For  genito-urinary  carriers 

(1)  Avoid  sexual  intercourse,  unless  with  protection. 

(2)  Do  not  marry  without  permission  of  a  physician. 

(3)  Take  regular  treatment. 

(4)  Have  periodic  examinations. 

d.  For  the  blood  carrier 

(1)  Avoid  bites  of  mosquitoes  by  screens  and  bed  nets. 

(2)  Kill  mosquitoes  found  in  room. 

(3)  Follow  lines  of  treatment. 

(4)  Have  periodic  examinations. 

D.  Vaccination.  This  is  one  of  the  best  all  around  measures  of 
preventive  medicine  as  the  chemistry  of  the  body  is  made  immune. 
This  immunity  is  of  course  effective  against  carrier  strains  as  well 
as  case  strains.  Its  limitations  lie  in  the  fact  that  there  are  many 
severe  diseases  against  which  no  vaccination  is  available  and  the 


114  CARRIERS   IN   INFECTIOUS   DISEASES 

fact  that  the  immunity  to  smallpox  and  typhoid  is  relative  and 
temporary.  The  immune  person  may  also  become  a  contact 
carrier,  but  this  condition  is  usually  temporaiy. 

The  combination  of  all  these  methods  is  very  effective  and 
prompts  the  enthusiast  to  draw  pictures  of  a  disease  free  world. 
The  place  of  carrier  work  in  this  program  should  neither  be  exag- 
gerated for  its  own  sake  nor  minimized  in  favor  of  other  measures. 
It  should  be  given  its  proper  value  in  the  major  project. 

2.  THE  METHOD  OF  CARRIER  WORK 

1.  The  first  and  most  obvious  place  to  start  carrier  work  is 
with  the  case.  If  a  case  can  be  diagnosed  by  demonstration  of  a 
parasite,  a  carrier  can  be  detected  by  the  same  methods.  The 
list  of  diseases  in  which  release  examinations  can  be  made  is  small 
in  comparison  to  the  total  number  of  diseases  but  large  in  com- 
parison to  actual  practise.  Some  few  diseases,  such  as  diphtheria, 
are  covered  by  law  or  regulations,  but  others,  as  typhoid,  are  left 
to  the  practitioner's  judgment.  A  great  advance  wiU  be  made  in 
carrier  work  when  release  cultures  are  insisted  on  whenever  pos- 
sible. Convalescence  has  several  advantages  for  carrier  work. 
There  is  usually  plenty  of  time  for  careful  examination.  Early 
diagnosis  is  possible  before  any  harm  is  done  and  treatment  is 
easier,  as  it  joins  on  to  the  treatment  of  the  case. 

A  single  adequate  examination  after  an  infectious  disease  would  be 
sufficient  to  dispose  of  the  carrier  question.  For  example,  a  single 
adequate  examination  of  bile  ducts  after  typhoid,  or  of  the  naso- 
pharynx after  diphtheria  or  meningitis  would  in  the  great  majority 
of  cases  be  sufficient,  but  usually  specimens  and  examinations  are 
more  or  less  inadequate.  Several  release  examinations  are  there- 
fore wisely  insisted  on.  The  specimens  should  be  taken,  if  neces- 
sary, by  a  "phorologist"  who  is  interested  in  finding  the  parasite, 
rather  than  by  a  physician  who  may  be  chiefly  interested  in  re- 
ceiving a  negative  laboratory  report. 

2.  The  next  logical  step  is  to  examine  contacts.  This  examina- 
tion has  a  double  object.  On  the  one  hand,  it  may  be  possible 
to  pick  up  the  carrier  who  has  caused  the  case  in  question,  or,  on 
the  other  hand,  it  may  be  possible  to  diagnose  other  carriers  who 
have  been  infected  by  the  case.     The  extent  to  which  this  work 


PHOROLOGY  AND  PREVENTIVE  MEDICINE         115 

should  be  carried  must  be  determined  by  the  indications  and  com- 
mon sense.  The  problem  is  fairly  easy  in  a  small  group  such  as  a 
family,  but  becomes  more  difficult  in  schools,  offices  and  among 
troops.  As  laboratory  facilities  increase,  this  phase  of  the  work 
tends  to  increase.  As  experience  increases,  we  will  be  more  able 
to  give  a  more  exact  program. 

3.  In  addition  to  the  case  and  the  contacts  there  are  several 
general  measures  which  are  practical  and  valuable.  The  first 
of  these  is  the  examination  of  special  groups  such  as  food  handlers. 
If  the  amount  of  sickness  due  to  ignorant  and  careless  servants 
were  accurately  known,  it  would  probably  be  a  shock  to  most 
people.  The  worst  conditions  are  usually  found  in  the  colored 
races.  Public  eating  places  as  well  as  homes  are  subject  to  con- 
tamination in  this  way.  These  examinations  should  relate  pri- 
marily to  intestinal  carriers,  but  milkmen  should  be  examined  for 
diphtheria  carriers  and  possibly  streptococcus  carriers. 

4.  Another  practical  line  of  carrier  attack  is  in  applicants  for 
positions.  They  are  usually  subject  to  some  examination  and  the 
common  carrier  conditions  can  gradually  be  included.  As  more 
exact  methods  are  becoming  available  for  the  evaluation  of  the 
individual,  it  is  being  realized  as  never  before  that  a  real  examina- 
tion should  include  the  whole  organism,  mental  and  physical. 
If  we  go  one  step  farther  and  view  the  individual  as  a  social  being, 
it  is  also  indicated  to  determine  whether  he  is  a  carrier.  The 
actual  examinations  to  be  made  should  depend  on  previous  sick- 
ness, the  nature  of  the  work  and  the  prevailing  diseases.  Under 
varying  conditions  these  examinations  should  include  the  follow- 
ing procedures:  (1)  A  nose  and  throat  swab  could  be  made  and 
blood  serum  tubes  could  be  inoculated  for  growth  of  the  diphtheria 
bacillus.  (2)  A  tonsil  swab  could  be  made  and  the  specimen 
examined  on  a  blood  agar  plate  for  hemolytic  streptococci.  (3) 
A  nasopharyngeal  swab  could  be  made  and  the  material  examined 
on  laked  blood  agar  plates  for  meningococci.  (4)  The  saliva  could 
be  examined  for  pneumococci  by  the  mouse  method.  (5)  The 
feces  and  urine  could  be  examined  for  typhoid  group  of  bacilH. 
(6)  The  feces  could  be  examined  for  the  organisms  of  cholera  and 
dysentery.  (7)  A  blood  film  could  be  examined  for  malarial 
gametes  or  filaria. 


116  CARRIERS   IN   INFECTIOUS   DISEASES 

5.  A  similar  time  and  place  for  carrier  work  is  at  the  regular 
physical  examinations  which  are  becoming  more  and  more  fre- 
quent. These  examinations  are  usually  made  for  the  personal 
benefit  of  the  individual  but  should  be  broadened  to  include  the 
welfare  of  the  group.  The  success  of  the  work  would  depend 
naturally  on  the  common  sense  and  care  with  which  it  was  planned. 

6.  A  special  case  is  presented  by  carriers  in  the  venereal  dis- 
eases. Recently  a  demand  for  premarital  examinations  has  arisen 
to  meet  this  situation.  In  spite  of  its  difficulties  this  movement  is 
a  real  advance.  It  calls  for  examinations  for  syphilis,  including 
the  Wassermann  reaction,  and  examination  for  the  gonorrhea, 
including  specimens  of  prostatic  secretions.  If  these  examina- 
tions were  more  general  and  if  appropriate  action  followed  the 
results,  the  number  of  social  tragedies  and  divorces  would  be 
appreciably  reduced. 

3.    CARRIER   WORK   IN   THE   MILITARY    SERVICES 

On  the  technical  side,  carrier  work  in  the  military  services  is 
of  course  the  same  as  elsewhere,  as  the  putting  of  a  uniform  on  the 
host  does  not  affect  the  parasite.  There  are,  however,  several 
special  factors  in  epidemiology  and  administration  among  soldiers 
which  do  affect  the  work  in  a  peculiar  way.  Personal  contact  is 
much  closer  and  more  constant  among  troops  in  barracks  or  in  the 
field  than  among  private  citizens.  Hence,  the  chances  for  the 
functioning  of  carriers  are  particularly  good.  On  the  other  hand, 
diagnostic  and  control  measures,  when  approved,  can  be  carried 
out  more  exactly  on  account  of  military  discipline.  Again,  the 
high  standard  of  laboratory  facilities  which  has  been  maintained 
in  the  United  States  Army  since  the  days  of  Sternberg  tends  to 
make  carrier  work  easier  than  in  some  other  places.  It  may, 
therefore,  be  said  that  conditions  in  the  Army,  and  the  same  is 
true  of  the  Navy,  offer  unusual  need  and  opportunity  for  carrier 
work.  The  drawbacks  are  lack  of  time  for  proper  examination, 
lack  of  facilities  for  the  mass  of  work  and  lack  of  control  due 
either  to  an  emergency  or  to  official  non-support. 

Beginning  with  the  case,  release  examinations  can  usually  be 
made  with  certainty.  Regulations  insure  the  sending  of  speci- 
mens to  the  laboratory  and  the  laboratory  work  is  usually  prompt 


PHOROLOGY   AND    PREVENTIVE    MEDICINE  117 

and  reliable.  In  fact,  three  release  cultures  of  feces  and  urine 
after  typhoid  infections  have  been  made  for  years  in  the  Army 
as  a  result  of  the  early  efforts  of  Russell.  The  Malarial  Register, 
introduced  by  Craig,  has  also  served  to  emphasize  the  carrier 
aspects  of  malaria.  Release  cultures  are  also  of  course  made 
routinely  in  convalescents  from  diphtheria  and  should  be  the 
rule  after  meningitis,  dysentery  and  cholera. 

After  an  epidemic,  the  number  of  temporary  convalescent 
carriers  may  be  so  large  as  to  be  a  problem.  It  may  be  necessary 
to  send  men  to  duty  as  soon  as  possible,  but  carriers  should  be 
held  if  possible  until  clean.  The  alternative  of  discharge  for 
disability  should  be  taken  only  as  a  last  resort.  A  pubHc  service 
owes  it  to  the  individual  and  to  the  country  to  do  as  much  as  pos- 
sible for  the  carrier  state.  If  discharge  becomes  necessary,  the 
public  health  officials  of  the  place  to  which  the  man  goes  should 
be  notified. 

Recruits  offer  a  large  opportunity  for  carrier  work.  It  is  being 
realized  more  than  ever  that  the  raw  recruit  is  first  of  allamedical 
problem.  He  should  be  examined  for  mental  and  physical  suita- 
bihty;  minor  defects  should  be  corrected.  He  should  be  immu- 
nized against  smallpox  and  the  typhoid  fevers.  Wassermann 
reactions  have  been  done  routinely  in  the  past  and  Schick  tests 
are  now  in  order.  Altogether  about  two  weeks  time  could  be 
taken  up  by  the  medical  officers  in  preparing  the  recruit  for  the 
work  in  hand.  The  preparation  of  a  recruit's  tissues  by  the  cor- 
rection of  defects  and  the  training  of  his  immune  mechanism  by  the 
medical  officer  is  as  necessary  as  the  training  of  his  neuromus- 
cular apparatus  or  his  morale  by  the  line  officer.  Carrier  work 
is  another  measure  of  preparation  for  social  enterprises.  The 
detection  of  carriers  should  be  done  early  in  order  to  pick  up 
chronic  convalescent  carriers  before  any  harm  is  done.  On 
account  of  the  numbers,  it  may  be  necessary  to  confine  the 
examination  to  those  who  give  a  previous  history  of  diphtheria, 
meningitis,  typhoid  or  dysentery  or  malaria,  or  who  come  from 
infected  districts. 

When  cases  occur,  the  examination  of  contacts  is  indicated,  but 
its  degree  of  application  is  a  difficult  question.  A  complete  ex- 
amination is  of  course  the  logical  measure,  but  it  is  usually  out  of 


118  CARRIERS  IN  INFECTIOUS  DISEASES 

the  question  and  practical  experience  shows  that  other  less  radical 
measures  are  sufficient.  Attempts  to  examine  contacts  should 
usually  be  confined  to  immediate  contacts  only,  unless  the  group 
is  small,  or  unless  the  laboratory  facihties  are  unusual,  or  unless 
other  measures  fail,  such  as  general  sanitation  and  hygiene. 

In  any  effective  carrier  work,  some  continuous  record  is  neces- 
sary by  which  a  chronic  carrier  can  be  checked  up  by  different 
medical  officers  under  whose  observation  he  may  come.  In  the 
Navy,  the  Health  Record  would  serve  admirably  for  this  purpose. 
The  Army  has  as  yet  no  record  of  this  kind,  except  the  Syphilitic 
and  Malarial  Registers.  Efforts  to  introduce  a  Health  Record 
have  so  far  been  defeated  by  the  amount  of  work  necessary  for 
keeping  it  properly.  There  is,  however,  the  individual  Service 
Record  which  has  in  the  past  had  some  data  on  vaccination.  It 
has  now  been  decided  to  give  more  space  for  medical  records  which 
will  include  a  place  for  carrier  examinations.  In  this  way  the  car- 
rier status  of  the  individual  can  be  checked  up  by  each  medical 
officer  who  reviews  the  records. 

During  the  war,  carrier  work  eventually  reached  a  high  state  of 
technical  perfection  as  so  many  well  trained  medical  officers  and 
assistants  were  available.  The  degree  to  which  the  carrier  pro- 
gram was  actually  used  to  control  the  situation  varied  with  the 
circumstances.  Now  that  the  military  estabhshments  are  con- 
tracted to  a  peace  basis,  this  work  has  necessarily  become  Umited. 
But  since  the  work  of  the  mihtary  organizations  is  now  largely 
educational  in  connection  with  National  Guard  and  the  Reserves, 
the  principles  learned  should  not  be  forgotten.  This  new  knowl- 
edge should  be  applied  on  as  large  a  scale  as  possible,  as  a  measure 
of  education  and  preparation. 


PART  IV 

CARRIERS  IN  VETERINARY 
MEDICINE 


CARRIERS  IN  VETERINARY  MEDICINE 

Carriers  of  the  specific  organisms  of  various  infectious  diseases 
met  with  in  veterinary  medicine  have  for  a  number  of  years  been 
recognized  among  domestic  animals.  However,  there  is  a  marked 
paucity  of  hterature  treating  of  the  subject  generally.  As  a 
matter  of  fact,  so  far  as  I  have  been  able  to  ascertain,  there  is  not 
a  single  work  published  in  Enghsh,  French  or  German,  dealing 
collectively  with  carriers  of  disease-producing  organisms  of  veteri- 
nary subjects. 

On  the  other  hand,  the  carrier  problem  in  a  number  of  infectious 
maladies  of  domestic  animals  has  been  given  careful  consideration 
in  studies  of  the  individual  diseases,  and  from  our  present  know- 
ledge of  the  subject,  thus  gained,  it  is  clearly  evident  that  carriers 
among  veterinary  subjects  present  a  problem  equal  in  impor- 
tance to  that  in  human  medicine.  Further,  in  numerous  in- 
stances the  animal  carrier  is  a  distinct  menace  to  the  health  of 
human  beings,  so  that  often  the  problem  is  not  only  one  of  pre- 
vention of  disease  among  lower  animals,  but  of  safeguarding  the 
health  of  man  as  well. 

For  purpose  of  consideration  in  this  section,  carriers  have  been 
arranged  in  three  principal  groups.  The  first  group  includes 
carriers  of  organisms  known  to  be  pathogenic  for  man  as  well  as 
for  the  lower  animals.  The  second  group  deals  with  carriers  of 
organisms  which  are  pathogenic  for  lower  animals  and  which  may 
possibly  prove  pathogenic  for  man  under  certain  circumstances. 
The  third  group  includes  carriers  of  organisms  pathogenic  for 
animals  only.  Under  each  main  group  are  then  taken  up  (1) 
carriers  of  bacteria,  (2)  carriers  of  protozoa  and  (3)  carriers  of 
filterable  viruses. 


121 


CHAPTER  XVII 

Carriers  of  Organisms  Pathogenic  for  Both  Man  and 
The  Lower  Animals 

A.  carriers  of  bacteria 

1.  Micrococcus  melitensis 

"Mediterranean,"  "Rock,"  "Undulant"  or  "Malta"  fever  in 
man,  caused  by  Micrococcus  melitensis,  has  for  an  indefinite 
period  been  more  or  less  endemic  on  the  Island  of  Malta.  The 
disease  has  also  been  reported  from  Italy,  Greece,  Turkey,  Spain, 
India,  Africa  and  the  Philippine  Islands.  In  the  United  States 
it  has  occured  in  Texas  along  the  Mexican  border.  The  affection 
is  primarily  a  disease  of  goats.  Sheep,  horses  and  cattle,  however, 
are  occasionally  affected. 

From  the  standpoint  of  carriers,  Malta  fever  presents  a  highly 
important  problem  in  those  locahties  where  the  disease  exists,  as 
the  infection  is  ordinarily  transmitted  to  man  through  the  inges- 
tion of  milk  from  animals  harboring  Micrococcus  melitensis  in 
their  udders. 

Zammit  (1)  demonstrated  that  approximately  10  per  cent  of 
the  goats  on  the  Island  of  Malta,  though  apparently  healthy, 
were  eliminating  the  micrococcus  of  Malta  fever  with  their  milk. 
Such  milk,  when  fed  to  monkeys,  even  for  one  day,  produced 
typical  attacks  of  the  disease,  the  manifestations  of  the  affection 
in  such  animals  closely  resembling  the  symptoms  noted  in  the 
disease  in  man. 

Carriers  also  eliminate  the  organism  irregularly  in  their  urine. 
The  disease  may  thus  be  readily  transmitted  to  healthy  animals 
through  the  ingestion  of  feed  and  water  contaminated  with  the 
urine  of  carriers. 

Mohler  and  Hart  (2),  in  reporting  the  finding  of  carriers  in  an 
importation  of  65  goats  from  the  Island  of  Malta  to  the  United 
States  in  1905,  state  that  out  of  12  persons  who  were  known  to  have 

133 


124  CARRIERS   IN   INFECTIOUS   DISEASES 

consumed  milk  from  these  goats  during  the  voysige  to  this  country, 
8  developed  Malta  fever.  The  diagnosis  was  confirmed  in  5 
cases  by  the  agglutination  test,  blood  specimens  not  being  obtained 
from  the  other  3  cases.  The  4  individuals  who  failed  to  contract 
the  disease  drank  only  a  small  amount  of  the  milk  or  partook  of 
it  only  after  it  had  been  heated. 

Upon  arrival  in  the  United  States  the  goats  in  this  shipment 
were  placed  in  quarantine  and  specimens  of  their  blood  serum 
subjected  to  the  agglutination  test  for  Malta  fever.  Twenty 
positive  and  suspicious  reactions  were  obtained.  Subsequently 
positive  results  were  obtained  with  specimens  from  a  number  of 
those  animals  whose  blood  had  given  negative  results  to  the  first 
test. 

The  milk  of  8  typically  positive  reactors  was  examined  bacterio- 
logically  and  Micrococcus  melitensis  demonstrated  in  large  num- 
bers in  4  cases.  The  milk  of  these  animals  appeared  absolutely 
normal  and  failed  to  show  evidence  of  changes  even  on  chemical 
examination.  Examination  of  the  urine  revealed  the  organism 
in  1  out  of  11  cases  studied. 

Habitat  of  the  organism.  Micrococus  melitensis  in  the  body  of 
carriers  lives  a  passive  existence.  In  localities  where  the  disease 
is  prevalent  a  large  percentage  of  goats,  and  in  some  instances 
sheep,  harbor  the  organism  in  their  udders,  usually  without 
changes  in  the  gland  tissue.  In  a  number  of  cases  the  micrococcus 
is  also  found  in  the  blood  of  apparently  healthy  animals  and  is 
eliminated  in  the  urine.  Rarely  the  organism  is  foimd  in  the 
intestinal  tract. 

Occasionally  autopsy  of  carriers  of  the  organism  may  demon- 
strate a  shght  fibrinous  inflammation  of  the  udder  and  in  some 
few  cases  purulent  foci.  The  spleen  and  certain  of  the  lymph 
nodes,  particularly  the  mesenteric  and  inguinal  glands,  may  be 
found  slightly  swollen. 

Detection  and  management.  Carriers  of  Micrococcus  meHtensis 
maj^  be  detected  through  the  application  of  the  agglutination  test 
and  bacteriological  examination  of  the  milk,  blood  and  urine  of 
suspected  animals.  Saisawa  (3)  utilized  the  complement-fixation 
test  for  the  detection  of  the  infection.  However,  because  of  its 
relative  simpHcity,  the  agglutination  test  is  more  adaptable. 


ORGANISMS   PATHOGENIC    FOR  MAN   AND   ANIMALS  125 

In  carrying  out  the  agglutination  test  either  blood  or  milk  serum 
may  be  used.  Blood  serum,  however,  is  preferable.  Mohler  and 
Hart  (2),  after  comparing  the  agglutinating  titre  of  blood  serum 
from  normal  and  infected  goats,  considered  complete  agglutina- 
tion within  one  and  one-half  hours  in  a  dilution  of  at  least  1 :  70,  a 
positive  reaction. 

Several  years  ago  Evans  (4),  in  calling  attention  to  the  very 
close  relationship  of  Bacterium  abortus  (Bang)  to  Micrococcus 
mehtensis,  pointed  out  that  the  serum  of  cattle  infected  with  the 
Bang  organism  readily  agglutinates  the  micrococcus  of  Malta 
fever.  While  at  present  there  is  no  evidence  that  goats  are  com- 
monly infected  with  Bact.  abortus,  the  possibility  of  positive 
reactions  in  some  instances  being  due  to  infection  with  the  bac- 
terium of  Bang,  should  be  borne  in  mind  when  carrying  out  the 
agglutination  test  for  Malta  fever. 

For  the  bacteriological  examinations  a  nutrose  agar  containing 
beef  serum  and  of  a  slightly  acid  reaction,  is  best  adapted  for  the 
isolation  of  the  organism.  The  growth,  however,  is  rather  slow. 
Seventy-two  hours  or  longer  are  required  before  the  colonies  are 
discernible  to  the  naked  eye. 

Animals  found  to  be  carriers  of  Micrococcus  melitensis  are  a 
menace  to  the  health  of  both  man  and  animals.  In  local- 
ities where  the  disease  is  not  well  estabhshed  its  spread  should  be 
guarded  against  by  the  prompt  destruction  of  cases  and  carriers. 

Where  the  disease  is  well  established  and  a  great  number  of  the 
annuals  are  infected,  slaughter  of  carriers  is  not  always  feasible. 
In  such  cases  the  disease  can  only  be  controlled  by  the  inaugura- 
tion of  measures  to  prevent  direct  or  indirect  contact  of  carriers 
with  healthy  animals. 

As  the  disease  in  man  is  due,  in  essentially  all  instances,  to  the 
consumption  of  milk  containing  the  organism,  it  is  highly  im- 
portant that  milk  from  known  or  suspected  carriers  of  Micrococcus 
melitensis  be  properly  pasteurized. 

2.  Bacillus  tuberculosis 

The  disseminator  of  bovine  tubercle  bacilli  is  a  serious  menace 
to  the  health  of  man  because  of  the  susceptibility  of  young  persons 
to  infection  with  this  type  of  the  organism.     In  the  vast  percen- 


126  CARRIERS  IN  INFECTIOUS  DISEASES 

tage  of  cases  the  infection  is  transmitted  through  milk.  Trans- 
mission of  tuberculosis  from  animal  to  man  through  the  ingestion 
of  infected  meat,  or  meat-food  products  into  the  preparation  of 
which  may  have  entered  glands  or  other  tissues  containing  the 
organism,  is  very  rare.  In  the  first  place  the  large  percentage  of 
meat  consumed  is  cooked.  Further,  meat  does  not  form  a  part  of 
the  ordinary  diet  of  young  children.  Where  eaten  uncooked  by 
adults,  chance  of  infection  is  slight,  because  of  the  resistance  of  older 
persons  to  the  infection  with  the  bovine  type  of  tubercle  bacilli. 
Where  vaccination  of  animals  with  human  tubercle  bacilh,  as  later 
described,  is  attempted,  we  have  a  different  situation.  In  such 
instances  the  organism  eliminated  by  vaccinated  animals  is  capable 
of  producing  tuberculosis  in  both  children  and  adults. 

In  tuberculosis  we  frequently  meet  with  cattle  which  clinically 
manifest  themselves  as  carriers  but  which  are  in  reality  occult 
cases  of  the  disease.  Such  cases  are  often  noted  among  dairy 
cows.  Animals  apparently  in  the  pink  of  condition  have  been 
known  to  eliminate  tubercle  bacilli  with  their  milk  intermittently 
for  years,  the  only  indication  of  disease  being  a  positive  response 
to  the  tubercuhn  test.  In  other  cases  of  this  character  tubercle 
bacilli  are  eliminated  periodically  for  years  with  the  feces,  as  a 
result  of  an  occult  pulmonary  affection.  In  such  instances  the 
animal  swallows  material  from  the  lungs  containing  the  organism 
and  passes  it  through  the  digestive  tract.  Autopsy  of  these  cases 
demonstrates  open  lesions  of  a  progressive  nature.  Animals 
coming  into  this  category,  when  permitted  to  live  for  a  consider- 
able time,  as  a  rule,  subsequently  manifest  evidence  of  the  disease 
and  on  autopsy  well-marked  lesions  of  tuberculosis,  frequently 
generalized,  are  found.  These  cases  cannot,  therefore,  be  con- 
sidered true  carriers. 

There  is  another  condition  met  with  in  cattle  in  which  certain 
animals  may  more  properly  be  considered  true  carriers  of  the 
tubercle  baciUus.  Not  infrequently,  autopsy  of  cattle  which 
have  reacted  to  the  tuberculin  test,  fails  to  demonstrate  appreci- 
able lesions  of  tuberculosis.  Bacteriological  examination  and 
guinea  pig  inoculations,  however,  frequently  demonstrate  that 
certain  of  the  l3Tiiph  glands  of  such  animals,  while  appearing  nor- 
mal, or  at  the  most  showing  only  minor  changes,  harbor  the  bacil- 


ORGANISMS    PATHOGENIC    FOR   MAN   AND   ANIMALS  127 

lus  of  tuberculosis.  Of  1296  specimens,  practically  all  of  which 
were  such  lymph  glands,  examined  by  the  United  States  Bureau  of 
Animal  Industry  (5)  during  the  fiscal  year  1921,  a  total  of  258  or 
nearly  20  per  cent  were  found  to  harbor  tubercle  bacilli.  Such 
carriers  are  not  a  menace  as  disseminators  of  the  infection,  but 
are  of  importance  from  the  standpoint  that  they  may  later  pass 
from  what  might  be  termed  an  "incubationary  carrier"  state, 
develop  the  disease  in  a  pronounced  form,  and  then  become 
spreaders. 

Carriers  of  tubercle  bacilli  may  be  produced  in  dairy  cows  as  a 
result  of  attempts  at  artificial  immunization  against  tuberculosis. 
Some  years  ago  considerable  attention  was  paid  by  investigators 
of  animal  diseases  to  the  so-called  "bovo-vaccination"  of  cattle 
against  tuberculosis.  The  treatment  consisted  of  the  intravenous 
administration  of  human  tubercle  bacilli  which  were  not  fully 
virulent,  cattle  possessing  considerable  resistance  to  the  human 
type  of  organism.  While  such  procedure  materially  raises  the 
immunity  of  the  animal  to  bovine  tuberculosis,  a  lai^e  percentage 
of  such  cattle  were  found  to  harbor  and  eliminate  the  organism 
from  their  udders  for  years,  without  developing  manifest  lesions 
of  the  disease  themselves,  or  at  the  most  developing  very  minor 
lesions  after  tolerating  the  organism  for  a  long  period  of  time. 
Because  of  these  dangerous  carriers,  produced  as  a  result  of  this 
method  of  vaccination,  the  procedure  did  not  become  established 
in  the  United  States. 

The  tubercle  bacillus  is  frequently  found  in  various  of  the 
lymph  glands  of  hogs,  occurring  without  additional  lesions  in 
other  organs.  In  some  such  cases  little  or  no  abnormality  is 
noted  in  the  gland  structure.  In  other  cases,  however,  marked 
changes  are  found.  Thus,  as  scrofula  is  a  rather  characteristic 
form  of  the  disease  in  hogs,  it  is  difficult  to  distinguish  between 
what  might  properly  be  termed  a  carrier  and  an  early  case  of 
tuberculosis  of  the  glands.  The  bacillus  of  tuberculosis  has  also 
been  occasionally  found  in  the  tonsillar  crypts  in  hogs.  Their 
presence  in  such  location,  however,  is  usually  transitory. 

Habitat  of  the  organism.  In  those  carriers  among  cattle  which 
harbor  the  tubercle  bacillus  in  glands,  the  submaxillary,  cervical, 
prescapular,  mediastinal,  bronchial  and  mesenteric  nodes  are  the 


128  CARRIERS   IN   INFECTIOUS   DISEASES 

most  frequent  locations.  Such  glands  may  be  more  or  less  swollen 
and  show  small  inflamed  areas  in  the  cortical  substance. 

In  carriers  produced  as  a  result  of  vaccination  against  tuber- 
culosis no  detectable  lesions  may  be  found  on  autopsy,  although 
the  animal  may  have  been  eliminating  the  organism  frequently 
with  her  milk.  However,  after  a  considerable  period  of  time  (3  or 
4  years  in  some  instances)  small  atypical  tubercles  may  be  found 
in  the  udder. 

In  hogs  the  submaxillary  and  superior  cervical  glands  are  favor- 
ite habitats  of  the  organism.  The  bronchial,  gastro-hepatic  and 
mesenteric  glands  are  less  frequent  locations.  Where  these  glands 
show  lesions,  a  type  of  hyahne  degeneration  is  frequently  seen, 
cross  sections  of  such  glands  having  a  dendritic  or  arbor-vitae 
appearance.  In  other  instances  small  areas  of  inflammation  or 
small  yellow  foci  may  be  demonstrated  in  the  glands. 

Detection  and  management.  The  subcutaneous,  intradermic  or 
ophthalmic  tuberculin  tests,  or  combinations  of  the  same,  consti- 
tute the  only  means  at  our  disposal  for  the  detection  of  the  carrier 
type  of  animal  harboring  Bacillus  tuberculosis  in  its  glands. 
Obviously,  however,  such  tests  will  not  differentiate  these  carriers 
from  the  more  marked  cases  of  tuberculosis.  Further,  while  a 
considerable  percentage  of  animals  carrying  the  organism  in  their 
lymph  glands  will  respond  to  the  tubercuhn  test,  negative  results 
are  undoubtedly  obtained  in  a  percentage  of  such  cases. 

Where  vaccination  against  tuberculosis  has  been  practiced, 
bacteriological  examinations  and  guinea  pig  inoculation  tests  with 
milk  specimens  from  suspected  carriers,  prove  satisfactory^  for 
their  detection.  These  tests  must  be  frequently  repeated,  how- 
ever, where  negative  results  are  obtained,  before  concluding  that 
the  animal  is  not  eliminating  the  organism.  Some  of  these  car- 
riers will  also  give  a  positive  response  to  the  tuberculin  test. 

The  prompt  slaughter  of  cattle  and  hogs  known  to  harbor  the 
tubercle  bacillus  is  the  practice  to  be  recommended.  Except  in 
cases  of  valuable  breeding  stock,  such  hogs  would  ordinarily  be 
butchered  as  an  economic  procedure.  With  cattle,  however,  this 
method  cannot  always  be  carried  out  because  of  the  common 
practice  of  a  large  number  of  dairymen  to  maintain  herds  con- 
taining tuberculous  cows.     Under  such  conditions  rigid  measures 


ORGANISMS   PATHOGENIC    FOR   MAN   AND   ANIMALS  129 

should  be  taken  to  prevent  the  exposure  of  healthy  animals  to  these 
carriers  of  tubercle  bacilli. 

Because  of  the  pathogenicity  of  the  bovine  type  of  tubercle 
bacillus  for  children,  and  the  part  that  milk  can  play  in  the  trans- 
mission of  the  infection,  pasteurization  of  milk  from  herds  in 
which  there  are  animals  known  or  suspected  of  harboring  the 
bacillus  of  tuberculosis  is  obviously  of  utmost  importance. 

3.  Organisms  of  the  Salmonella,  Enteritidis  or  Gaertner  group 

Bacillus  enteritidis  (Gaertner),  Bacillus  paratyphosus  "B," 
Bacillus  suipestifer,  Bacillus  aertrycke,  and  other  members  of  the 
Salmonella  group,  have  at  different  times  been  found  associated 
with  a  variety  of  pathological  conditions  in  cattle,  horses,  sheep, 
hogs  and  other  animals.  Further,  carriers  of  these  organisms 
have  been  frequently  found  among  animals  which  have  recovered 
from  such  affections,  as  well  as  in  animals  with  no  history  of  dis- 
ease. Because  of  the  role  organisms  of  this  group  play  in  the 
production  of  "food-poisoning"  in  man,  carriers  of  the  same  are 
of  particular  importance. 

B.  enteritidis  has  been  occasionally  found  associated  with  severe 
cases  of  dysentery,  especially  in  calves,  although  adult  cattle 
are  sometimes  affected.  Mohler  and  Buckley  (6)  in  1902  found 
B.  enteritidis  to  be  the  etiological  factor  in  an  outbreak  of  enteritis 
with  marked  symptoms  of  intoxication,  in  a  stable  of  twenty-one 
cows.  This  organism  has  also  been  found  in  pathological  condi- 
tions of  the  udder,  persisting  in  some  cases  for  considerable  periods 
of  time  after  the  disease  process  has  subsided. 

In  hogs,  Bacillus  suipestifer  is  found  as  a  complicating  factor 
in  cholera,  the  primary  cause  of  the  disease  being  a  filterable  virus. 
Carriers  of  this  bacillus  are  very  frequently  found. 

Among  experimental  animals  the  writer  has  noted  an  outbreak 
of  disease  among  guinea  pigs  due  to  Bacillus  aertrycke,  in  which 
carriers  of  the  organism  were  subsequently  found.  O'Brien  (7) 
records  an  epizootic  among  stock  guinea  pigs  at  the  Lister  Institute 
due  to  an  organism  which  he  identified  as  B.  suipestifer.  Subse- 
quent to  the  outbreak  he  demonstrated  5  of  the  recovered  animals 
to  be  carriers,  eliminating  the  organism  intermittently  for  five 
months. 


130  CARRIERS  IN  INFECTIOUS   DISEASES 

Members  of  this  group  of  organisms  are  occasionally  responsible 
for  outbreaks  of  disease  among  rodents.  Further,  healthy  rats 
and  mice  are  often  found  to  be  carriers  of  the  bacilU  of  this  group, 
eliminating  the  same  with  their  feces.  Because  of  the  opportunity 
afforded  for  the  contamination  of  foodstuffs  with  fecal  matter 
from  rats  and  mice  around  abattoirs,  refrigerator  plants,  butcher 
shops,  etc.,  these  carriers  are  of  no  little  importance. 

Heuser  (8)  examined  100  mice  and  found  5  or  5  per  cent  har- 
boring B.  enteritidis  and  B.  paratyphosus  "B."  Zwick  and 
Weichel  (9)  in  examining  177  mice  demonstrated  28  or  nearly 
16  per  cent  to  be  carriers  of  organisms  of  the  Salmonella  group. 

Meissner,  Berge  and  Kohlstock  (10)  report  an  interesting  out- 
break of  dysentery  among  calves  due  to  B.  enteritidis.  One  of  the 
recovered  animals  was  placed  in  a  pasture  with  a  number  of  cows 
and  shortly  thereafter  the  disease  broke  out  among  the  adult 
animals.  The  recovered  calf  was  then  examined  and  was  found 
to  be  harboring  B.  enteritidis  in  its  intestinal  tract. 

Outbreaks  of  food-poisoning  in  man  in  a  number  of  instances 
have  been  definitely  traced  to  animals  disseminating  organisms  of 
this  group.  Savage  (11)  described  an  outbreak  of  food-poisoning 
occurring  at  Newcastle-under-Ljnne  in  1914,  in  which  468  cases 
with  2  deaths  occurred.  The  malady  was  found  to  be  due  to  B. 
enteritidis  in  milk  consumed  by  the  affected  individuals.  Inves- 
tigation proved  the  source  of  the  infection  to  be  a  cow  which  had 
recently  calved,  and  which  had  an  udder  affection  and  abscesses 
in  one  of  its  legs.  The  serum  of  this  animal  readily  agglutinated 
B,  enteritidis.  Subsequent  examination  demonstrated  B.  enter- 
itidis in  the  urine  and  uterine  discharge.  After  the  outbreak  a 
number  of  specimens  of  milk  from  this  cow  were  examined  and  on 
two  occasions  B.  enteritidis  was  isolated. 

Aside  from  those  cases  in  which  organisms  of  the  enteritidis 
group  may  be  eliminated  with  the  milk,  contamination  with  fecal 
matter  often  occurs  at  the  time  of  milking  through  the  dropping 
of  particles  of  manure  from  the  hair  of  cows  which  have  not  been 
properly  cleaned,  or  through  splashing  at  the  time  of  defecation. 

As  regards  meat,  ample  opportunity  is  often  afforded  for  fecal 
contamination  of  such  food  in  the  slaughter-house  during  the 
course  of  its  preparation.     Thus  carriers  harboring  members  of 


ORGANISMS   PATHOGENIC    FOR   MAN   AND   ANIMALS  131 

this  group  of  organisms  in  their  intestinal  tracts  may  infect  their 
own  tissues  or  those  of  other  animals  at  the  time  of  slaughter, 
thereby  indirectly  menacing  the  health  of  man. 

Habitat  of  the  organism.  In  the  larger  percentage  of  cases, 
carriers  of  organisms  of  the  SahnoneUa  group  harbor  the  same  in 
their  intestines,  usually  without  appreciable  tissue  changes  in  the 
carrier  state.  Occasionally,  small  necrotic  foci  containing  organ- 
isms of  this  group  have  been  demonstrated  in  the  spleen  and  liver 
of  cattle,  sheep  and  hogs. 

In  hogs  which  have  had  the  intestinal  form  of  cholera,  ulcers 
of  variable  size  (lental  to  as  large  as  a  quarter)  which  are  slow  to 
heal,  and  which  usually  harbor  B.  suipestifer,  are  often  found, 
especially  in  the  caecum  and  large  intestine.  These  ulcers  usually 
occur  as  round,  slightly  projecting  masses,  of  a  yellow,  brown,  or 
almost  black  color,  the  cut  surface  appearing  laminated  from  the 
periphery  towards  the  center.  Microscopically,  sections  cut  per- 
pendicularly through  the  ulcer  show  the  thickened  submucous 
tissue  to  contain  numerous  dilated  capillaries  and  a  large  number 
of  round  cells.  Above  this  is  a  thin  layer  of  deep  staining  amor- 
phous material.  The  uppermost  layer  is  made  up  of  necrotic 
material  containing  large  numbers  of  bacteria  of  different  type. 
B.  suipestifer  may  be  found  in  the  necrotic  material  and  frequently 
in  large  numbers  around  the  periphery  of  the  ulcer  between  the 
necrotic  and  healthy  tissue. 

Organisms  of  this  group  are  occasionally  found  in  the  udder, 
usually  following  some  type  of  udder  trouble  for  which  it  was 
responsible,  and  rarely  when  there  is  no  history  of  disease.  Where 
such  carriers  have  had  a  pathological  process  in  the  udder,  tissue 
changes,  characteristic  of  previous  glandular  inflammation,  fre- 
quently exist. 

In  the  B.  aertrycke  infection  noted  by  the  writer  the  organism 
was  found  harbored  in  the  gall  bladder.  The  walls  of  the  bladder 
in  most  instances  showed  a  marked  catarrhal  thickening. 

Detection  and  7nanagement.  Carriers  of  bacilli  of  the  Sal- 
monella group,  harboring  the  same  in  their  intestinal  tracts  and 
udders,  as  a  rule,  may  be  detected  through  the  employment  of 
ordinary  bacteriological  methods.  Repeated  examinations,  how- 
ever, must  be  made  in  some  instances  before  the  organism  can  be 


132  CARRIERS   IN   INFECTIOUS   DISEASES 

demonstrated.  The  agglutination  test  may  prove  of  some  help 
in  identifying  animals  suspected  of  carrying  certain  members  of 
the  group.  Further,  the  writer  was  able  to  obtain  complement- 
fixation  reactions  with  blood  serum  from  guinea  pigs  harboring 
B,  aertrycke  in  their  gall  bladders. 

Animals  known  to  be  carriers  of  organisms  of  the  Salmonella 
group  which  are  capable  of  producing  disease  in  other  animals, 
should  be  kept  isolated  until  they  are  proven  no  longer  a  menace. 
In  cases  in  which  the  organism  is  carried  in  the  udder,  irrigation 
with  mild  antiseptics  may  prove  of  value  in  eliminating  the  foci 
of  infection.  Occasionally  bacterins  or  vaccines  give  good  results. 
Administration  of  intestinal  antiseptics  has  been  resorted  to  in  an 
effort  to  eliminate  offending  organisms  harbored  in  the  intestines. 
Such  treatment,  however,  is  not  particularly  promising  of  results. 
The  slaughter  of  persistent  carriers  which  continually  cause 
trouble,  is  sometimes  the  most  economic  procedure. 

Particular  consideration  should  be  given  to  measures  for  the 
prevention  of  infection  of  man.  Milk  from  cows  harboring 
organisms  of  this  group  is  a  particularly  dangerous  food  for 
both  man  and  anunals.  It  should  be  remembered  that  Bacillus 
enteritidis  (Gaertner)  produces  a  toxin  which  is  unaffected  by 
pasteurization. 

Because  of  the  possibility  of  milk  becoming  contaminated  with 
particles  of  fecal  matter,  during  the  milking  process,  cows  know 
to  carry  organisms  of  the  Gaertner  group  in  their  intestinal  tracts 
are  dangerous  animals  to  supply  milk  for  human  use  and  should 
be  eliminated  as  a  source  of  milk  supply  while  thus  harboring  and 
eliminating  these  organisms. 

In  the  slaughtering  of  food-producing  animals  every  precaution 
should  be  taken  to  prevent  the  contamination  of  carcasses  with 
fecal  matter.  Particular  attention  should  be  given  to  measures  to 
prevent  meat  and  other  food  products  from  becoming  contami- 
nated with  the  excrement  of  rats  and  mice. 

4.  Bacillus  tetani 

The  horse  is  a  well-known  carrier  of  Bacillus  tetani.  Cattle, 
sheep  and  hogs,  however,  also  harbor  the  organism  in  their  intefe- 
tinal  tracts  and  ehminate  the  same  in  considerable  numbers  in 


ORGANISMS    PATHOGENIC    FOR   MAN   AND    ANIMALS  133 

their  feces.  Further,  it  has  been  demonstrated  that  the  tetanus 
bacillus  is  not  infrequently  carried  by  smaller  experimental  ani- 
mals (rabbits  and  guinea  pigs).  The  organism  has  a  very  exten- 
sive distribution  in  nature,  being  a  common  inhabitant  of  the 
soil,  especially  where  the  same  contains  manure,  particularly  that 
from  horses. 

It  is  the  opinion  of  some  investigators  that  soil  contains  the 
organism  only  after  receiving  deposits  of  manure  from  horses  or 
other  herbivora  harboring  B.  tetani,  or  where  it  is  indirectly  con- 
taminated with  drainage  from  areas  containing  manure  of  such 
carriers.  This,  however,  is  not  likely.  Because  of  the  large 
percentage  of  carriers  among  herbivora,  the  tetanus  bacillus  is 
found  more  abundantly  in  earth  containing  manure,  but  it  is 
nevertheless  found  in  soil  undoubtedly  free  from  such  fecal 
contamination. 

The  percentage  of  carriers  among  animals  in  different  locations 
varies  between  rather  wide  limits.  Park  and  Williams  (12)  state 
that  approximately  15  per  cent  of  horses  and  calves  in  the  vicinity 
of  New  York  City  harbor  the  tetanus  organism  in  their  intestines. 

On  various  stock  farms  it  is  often  notable  that  tetanus  almost 
invariably  follows  minor  wounds  not  properly  treated.  In  other 
localities  such  occurrence  of  the  disease  may  be  extremely  rare. 

Habitat  of  the  organism.  In  carriers  Bacillus  tetani  is  found  in 
the  intestinal  tract,  especially  in  the  large  intestine.  As  is  the 
case  with  a  number  of  organisms  harbored  in  the  intestines,  the 
tetanus  bacillus  under  normal  conditions,  causes  no  disturbance  in 
the  health  of  its  host  and  produces  no  change  in  the  intestinal 
tissue. 

While  the  horse  commonly  harbors  B.  tetani  it  is,  nevertheless, 
very  susceptible  to  tetanus.  This  type  of  carrier,  in  a  way,  is  a 
mechanical  carrier,  as  differentiated  from  the  immune  and  con- 
valescent types. 

Detection  and  management.  No  particular  difficulty  is  experi- 
enced in  demonstrating  the  tetanus  bacillus  in  the  excreta  of  car- 
riers by  bacteriological  examination  and  through  the  inoculation 
of  mice,  guinea  pigs  or  rabbits. 

It  is  obvious,  of  course,  that  with  tetanus  we  are  confronted  with 
an  organism  which  exists  practically  everywhere  and  of  which 


134  CARRIERS  IN  INFECTIOUS   DISEASES 

thousands  of  carriers  exist  and  are  coming  into  being  daily.  It 
is,  therefore,  highly  important  that  particular  attention  be  paid 
to  wounds  which  have  directly  or  indirectly  come  in  contact  with 
manure  and  soil  or  admixtures  of  the  same. 

5.  Bacillus  oedematis  maligni  {"Vibrion  septique") 

The  anaerobic  Bacillus  oedematis  mahgni,  or  "Vibrion  septique" 
as  it  was  called  by  Pasteur,  is  widely  distributed  in  nature  and  is 
frequently  found  in  the  intestinal  tracts  of  normal  cattle,  horses, 
sheep  and  hogs. 

Among  animals,  malignant  edema,  the  specific  disease  of  this 
organism,  frequently  results  from  the  infection  of  contused, 
lacerated,  incised  and  other  types  of  deep  wounds,  with  soil,  feces 
of  carriers,  or  other  material  containing  the  bacillus  of  malignant 
edema.  The  disease  sometimes  follows  castration  and  shearing. 
Further,  it  is  an  occasional  compUcation  of  difficult  parturition, 
where  help  is  given  the  animal  and  proper  precautions  are  not  taken 
to  prevent  the  introduction  of  infection  with  the  hands  and  in- 
struments. The  disease  also  occurs  in  man  following  the  con- 
tamination of  wounds  with  soil,  manure,  or  admixtures  of  the 
same. 

Habitat  of  the  organism.  Carriers  of  Bacillus  oedematis  maligni, 
as  stated  above,  harbor  the  organism  in  their  intestinal  tracts. 
Under  normal  conditions  the  bacillus  lives  a  purely  saprophytic 
existence  in  the  intestines  of  such  carriers,  producing  no  tissue 
changes  whatever  as  a  result  of  its  presence  there. 

Detection  and  management.  The  bacillus  of  mahgnant  edema 
can  usually  be  demonstrated  in  the  feces  of  carriers  through  ana- 
erobic cultural  methods  and  animal  inoculation  tests  without 
difficulty. 

As  this  organism  is  found  constantly  in  soil  and  is  carried  by 
a  large  number  of  animals  of  different  species,  sanitary  measures 
must  be  relied  upon  to  control  the  infection,  as  the  elimination  of 
carriers  is  obviously  impossible.  Particular  attention  should  be 
paid  to  severe  wounds  contaminated  with  manure  or  soil. 


ORGANISMS   PATHOGENIC    FOR   MAN   AND    ANIMALS  135 

6.  Bacillus  anthracis 

While  at  the  present  time  nothing  is  known  of  possible  carriers 
of  the  anthrax  organism  among  cattle,  horses  and  sheep,  it  has 
been  definitely  established  that  apparently  healthy  hogs  occa- 
sionally harbor  Bacillus  anthracis  in  various  of  their  lymph  glands. 

Fortunately,  the  organism  thus  locahzed  is  not  capable  of  being 
ehminated  continuously  to  the  outside  world.  However,  such 
carriers  are,  nevertheless,  of  considerable  importance;  first,  be- 
cause they  may  later  develop  the  disease  in  an  acute  form,  thus 
disseminating  the  infection,  and  secondly,  because  such  glands 
entering  into  the  preparation  of  "cured"  meat-food  products,  may 
produce  the  disease  in  man  consuming  such  food,  especially  when 
uncooked. 

Habitat  of  the  organism.  In  hogs  harboring  Bacillus  anthracis 
the  organism  is  found  most  frequently  in  the  mesenteric  group, 
often  only  a  single  gland  in  the  group  being  affected.  Less  fre- 
quently the  cervical  glands  may  be  the  seat  of  the  infection.  Oc- 
casionally the  bacillus  may  be  demonstrated  in  the  submaxillary 


Glands  containing  the  anthrax  organism,  as  a  rule,  are  more  or 
less  enlarged,  and  on  cross  section  they  appear  of  a  brick-red  color 
or  they  may  be  permeated  with  small,  grayish-yellow,  necrotic 
foci.  The  surrounding  connective  tissue  may  disclose  a  sero- 
edematous  infiltration. 

Detection  and  management.  In  the  absence  of  allergic  or  other 
specific  tests  for  anthrax,  it  is  impossible  to  detect,  during  hfe, 
hogs  which  may  be  carrying  the  anthrax  organism  in  their  lymph 
glands.  Consequently  we  are  without  means  to  prevent  the 
possible  introduction  of  such  carriers  in  the  midst  of  healthy  hogs. 

When  carriers  of  this  character  are  butchered  in  estabhshments 
where  meat  inspection  service  is  maintained,  the  veterinary  in- 
spector has  the  opportunity  to  detect  some  of  those  cases  which 
show  appreciable  lesions  of  the  glands.  However,  in  some  in- 
stances the  tissue  lesions  are  so  insignificant  they  may  escape 
detection.  It  is  obvious,  therefore,  that  in  order  to  prevent  the 
possible  infection  of  man,  the  added  safe-guard  afforded  by  thor- 
oughly cooking  various  "cured"  products  before  consumption,  is 
advisable. 


136  CARRIERS  IN  INFECTIOUS   DISEASES 

7.  Bacillus  mallei 

While  no  definite,  clear-cut  carrier  problem  has  been  recognized 
in  glanders,  this  disease  is  one  of  those  maladies  in  which  it  is 
occasionally  difficult  to  determine  whether  or  not  a  particular 
infection  can  properly  be  placed  in  the  category  of  carriers. 

Autopsy  of  animals  which  have  reacted  to  the  allergic  or  sero- 
logical tests  for  glanders,  frequently  reveal  in  the  lungs,  and 
occasionally  in  the  Hver  or  spleen,  glanders  nodules  in  an  inactive 
or  apparently  arrested  stage.  Sometimes  only  a  single  nodule  of 
such  character  is  found.  Very  frequently  it  is  impossible  to 
isolate  B.  mallei  from  some  of  these  lesions.  On  the  other  hand, 
in  some  of  these  arrested  cases  it  is  possible  to  demonstrate  the 
organism  bacteriologically  and  through  guinea  pig  inoculation. 
In  such  case  we  are  possibly  justified  in  concluding  that  the  animal 
in  which  this  type  of  lesion  was  found  was  a  carrier.  Should  it 
have  been  permitted  to  Kve  and  mingle  with  other  animals  it 
may  have  subsequently  initiated  an  outbreak  of  glanders  through 
development  of  the  disease  in  an  active,  communicable  form  from 
this  focus. 

Habitat  of  the  organism.  In  such  instances,  as  described  above, 
the  lesions  are  most  commonly  found  in  the  lungs.  However, 
they  are  occasionally  found  in  the  hver  or  spleen.  They  occur  as 
small,  gray,  shining  nodules,  rarely  larger  than  a  pea,  the  center 
often  appearing  pale  yellow  as  a  result  of  necrosis.  The  nodule  is 
walled  off  from  the  normal  structure  by  fibrous  tissue. 

It  is  often  very  difficult  to  differentiate  the  nodule  of  glanders 
from  those  caused  by  parasites.  Microscopically,  however,  eo- 
sinophiha  is  a  characteristic  finding  in  parasitic  nodules.  Fur- 
ther, in  parasitic  nodules  of  recent  origin  fragments  of  the  parasite 
may  often  be  demonstrated,  while  in  older  processes  there  is  usu- 
ally calcification.  Calcification  in  glanders  nodules  is  doubtful, 
a  number  of  investigators  maintaining  that  it  never  occurs.  It 
is  certainly  not  a  common  finding.  Demonstration  of  B.  mallei 
in  the  nodule,  of  course,  definitely  establishes  its  nature.  Failure 
to  demonstrate  the  organism,  however,  would  not  in  itself  prove 
that  the  lesion  was  not  that  of  glanders  but  obviously  eliminates 
it  from  consideration  as  a  carrier  lesion. 


ORGANISMS   PATHOGENIC    FOR   MAN   AND   ANIMALS  137 

Detection  and  management.  The  allergic  and  serological  tests 
must  be  depended  upon  for  the  detection  of  carriers  of  Bacillus 
mallei  as  here  considered.  Fortunately,  these  tests  give  excellent 
results  in  the  great  percentage  of  cases.  They  do  not,  of  course, 
differentiate  between  the  active  and  arrested  case.  However,  as 
the  destruction  of  both  active  and  inactive  cases  is  advisable,  this 
shortcoming  of  the  diagnostic  methods  at  our  disposal,  is  of  little 
consequence. 

Suspected  animals  should  be  tested  with  intradermic  or  ophthal- 
mic mallein,  and  in  the  case  of  suspicious  or  doubtful  reactors, 
serum  specimens  from  the  questionable  animals  should  be  sub- 
jected to  the  complement-fixation  and  agglutination  tests  for 
glanders.  A  positive  reaction  to  any  one  of  these  tests  warrants 
the  destruction  of  the  animal. 

8.  Bacillus  diphtheriae 

While  it  has  been  proven  beyond  all  doubt  that  true  diphtheria 
in  man  and  the  common  diphtheritic  affections  of  lower  animals, 
are  distinct  and  separate  entities,  diphtheria  due  to  infection  with 
the  Klebs-Loeffler  bacillus  occasionally  occurs  in  animals  coming 
in  contact  with  individuals  of  the  human  family  suffering  from  the 
disease.  Considerable  reference  is  made  in  the  hterature  to 
cases  of  diphtheria  occurring  in  cats,  dogs,  fowls,  etc.,  as  a  result 
of  infection  with  the  organism  of  human  diphtheria.  Further, 
occasional  transmission  of  the  disease  from  animal  to  man  has 
undoubtedly  occurred. 

From  the  standpoint  of  carriers,  the  house  cat  has  been  fre- 
quently incriminated.  No  information,  however,  is  available 
as  to  the  possible  length  of  time  the  organism  may  persist  in  the 
body  of  such  carrier. 

Savage  (13)  has  pointed  out  that  diphtheria-like  organisms 
may  often  have  been  taken  for  the  real  diphtheria  bacillus 
in  reports  of  cases  and  carriers  of  the  infection  among  cats 
where  the  bacteriology  of  the  case  was  not  thoroughly  worked  out. 
He  even  goes  so  far  as  to  conclude  that  it  has  not  been  satisfac- 
torily estabHshed  that  cats  develop  diphtheria  due  to  the  Klebs- 
Loeffler  bacillus  or  are  carriers  of  the  infection.  There  is,  however, 
ample  evidence  of  a  definite  nature  to  refute  such  conclusions. 


138  CARRIERS   IN   INFECTIOUS   DISEASES 

Simmons  (14)  reports  a  fatal  case  of  diphtheria  in  a  woman, 
apparently  contracted  from  a  cat  which  was  permitted  to  sleep 
in  her  bed.  The  cat  had  been  sick  about  a  week  before  the  woman 
became  ill.  It  had  a  croupy  cough,  was  unable  to  swallow  food 
and  continually  cried.  The  condition  persisted  for  approximately 
two  weeks  after  which  the  animal  appeared  to  improve.  Cultures 
from  the  throat  of  both  the  woman  and  cat  demonstrated  the 
presence  of  Klebs-Loeflfier  bacillus,  the  identity  of  the  organism 
in  both  instances  being  definitely  established  through  immuno- 
logic tests  carried  out  with  guinea  pigs  protected  with  diphtheria 
antitoxin.  The  cat  was  chloroformed  and  autopsied  and  B. 
diphtheria  recovered  from  a  lesion  in  the  nasal  fossa. 

A  second  cat  which  had  been  associated  with  the  animal  just 
referred  to,  was  found  to  harbor  true  diphtheria  bacilli  in  lesions 
of  the  vocal  cords. 

Habitat  of  the  organism.  Cats  which  are  found  to  be  carriers 
of  the  Klebs-Loeffler  bacillus,  harbor  the  organism  in  their  nose  or 
throat.  In  one  of  the  two  cases  described  by  Simmons,  a  small 
oval  ulceration,  covered  with  a  yellowish-gray  pseudomembrane, 
occurring  between  two  smaller  red  inflammatory  areas,  was  noted 
in  the  left  nasal  fossa.  In  the  second  case  described  by  this  au- 
thor, small,  elongated,  grayish-white  patches  of  pseudomembranes 
were  found  covering  ulcerations  of  the  vocal  cords.  These  patches 
were  surrounded  by  a  red  inflammatory  zone. 

Detection  and  management.  In  examining  cats  suspected  of  har- 
boring the  diphtheria  bacillus,  material  should  be  obtained  from 
the  throat  and  each  side  of  the  nose  with  sterile  swabs  and  3  or  4 
tubes  of  Loeffler's  serum  media  inoculated  with  each  swab.  These 
cultures  should  then  be  incubated  and  subjected  to  the  usual 
bacteriological  examination  for  Bacillus  diphtheriae,  care  being 
taken  not  to  mistake  pseudo-diphtheria  organisms,  frequently 
found,  for  the  Klebs-Loeffler  bacillus. 

Cats  demonstrated  to  be  carriers  of  the  organism  of  human 
diphtheria  are  obviously  a  menace  to  the  health  of  human  beings, 
especially  the  child  who  plays  with  the  animal.  Although  there 
are  no  records  of  the  isolation  and  treatment  of  such  carriers,  it 
is  probable  that  a  number  of  these  cases  would  clear  up  under 
proper  treatment.  However,  under  ordinary  circumstances, 
prompt  destruction  of  recognized  carriers  is  the  policy  to  follow. 


ORGANISMS   PATHOGENIC    FOR   MAN   AND   ANIMALS  139 

9.  Bacillus  pestis 

While  bubonic  plague  ordinarily  occurs  as  an  acute  affection  in 
rats,  in  localities  where  the  disease  is  endemic  apparently  healthy 
rats  may  occasionally  be  found  harboring  Bacillus  pestis  in  foci 
in  their  abdominal  viscera. 

The  Indian  Plague  Commission  (15),  in  examining  a  large 
number  of  rats  caught  in  two  villages  where  plague  had  recurred 
annually  without  discoverable  reinfection,  found  6  apparently 
healthy  animals  with  small  abscesses  in  their  abdominal  cavities, 
containing  virulent  plague  organisms.  These  rats  were  all  trap- 
ped within  two  months,  at  a  time  of  the  year  when,  so  far  as  could 
be  ascertained,  plague  did  not  exist  in  man  nor  rats  in  the  two 
villages  in  question. 

McCoy  (16)  found  13.8  per  cent  of  several  hundred  ground 
squirrels  examined  for  plague  lesions,  harboring  B.  pestis  in  puru- 
lent foci  in  one  or  more  lymph  glands,  with  no  additional  evidence 
of  disease.  In  squirrels  experimentally  infected,  similar  lesions 
(referred  to  by  McCoy  as  "residual  buboes")  were  observed  in  the 
majority  of  animals  which  survived  the  infection. 

Rats  and  squirrels  with  such  lesions  have  ordinarily  been 
looked  upon  as  chronic  cases.  Nevertheless,  without  drawing  the 
line  too  close,  the  animal  with  small,  entirely  locaUzed  lesions  of 
an  inactive  character,  which  give  rise  to  no  manifest  disturbance 
of  health,  may  properly  be  considered  a  type  of  carrier. 

From  present  knowledge,  it  is  difficult  to  say  just  how  much 
importance  should  be  attached  to  such  carriers  of  Bacillus  pestis. 
Apparently  they  are  not  a  serious  menace.  Whether  or  not  the 
organisms  persisting  in  these  abscesses  are  ever  capable,  under 
certain  conditions,  of  subsequently  inciting  an  acute  attack  of 
plague,  thus  permitting  of  its  spread,  is  a  matter  of  conjecture. 
However,  the  carcasses  of  rats  with  such  lesions,  dead  from 
some  other  cause,  may  be  eaten  by  susceptible  rats  and  thus  give 
rise  to  an  outbreak  of  the  disease. 

Habitat  of  the  organism.  The  lesions  of  Bacillus  pestis  in  rats 
harboring  the  organism,  are  usually  found  in  the  spleen,  liver, 
mesentery  and  pelvic  glands.  They  occur  as  small  abscesses  con- 
taining a  creamy  or  cheesy  pus.  Often  adhesions  are  found 
between  the  affected  area  of  the  spleen  and  the  mesentery. 


140  CARRIERS  IN  INFECTIOUS  DISEASES 

In  squirrels,  McCoy  found  the  median,  posterior  inguinal 
and  pelvic  glands  the  most  frequent  seat  of  the  infection.  Less 
frequently  lesions  were  found  in  the  cervical  and  axillary  glands. 
The  gland  may  appear  as  a  mass  of  slightly  yellowish  pus  as  large 
as  a  pea.  In  other  instances  the  purulent  mass  is  much  smaller, 
or  there  may  be  noted  only  a  few,  mustard-seed  size,  necrotic 
points. 

Detection  and  management.  Rats  and  squirrels  harboring  the 
plague  organism  in  these  chronic  lesions  have  not  been  noted  to 
manifest  appreciable  disturbances  of  health.  Obviously,  the  de- 
tection of  such  carriers  in  localities  where  plague  occurs  or  is 
suspected,  is  accomplished  by  the  examination  of  considerable 
numbers  of  trapped  or  shot  rats  and  squirrels.  Bacillus  pestis, 
ordinarily,  can  readily  be  demonstrated  in  the  lesion  bacteriologi- 
cally  and  through  animal  inoculation  tests. 

Rodents  carrying  B.  pestis  in  lesions  such  as  above  described, 
apparently  are  not  a  serious  menace,  and  no  special  means  have 
been  employed  for  the  control  of  such  cases.  However,  in  dis- 
tricts where  plague  has  existed,  the  possibility  of  recurrence 
through  such  animals  must  be  considered,  and  so  far  as  rats  are 
concerned,  should  serve  as  a  stimulus  for  continued  sanitation 
and  measures  contributing  to  the  extermination  of  rats,  even 
though  an  organized  extermination  campaign  is  not  in  progress. 

10.  Bacterium  tularense 

McCoy  (16)  in  examining  ground  squirrels  for  evidence  of 
plague,  found  lesions  which  could  have  readily  been  mistaken  for 
those  of  that  disease.  Subsequently  the  causative  organism  was 
isolated  by  McCoy  and  Chapin  (17)  and  named  Bacterium  tularense, 
they  adopting  such  name  because  it  was  in  squirrels  from  Tulare 
County,  Calif.,  that  the  disease  was  first  noted. 

Man  is  readily  susceptible  to  infection  with  this  organism  either 
by  insect  bites  or  direct  inoculation  into  abrasions.  A  local  lesion 
is  produced  with  glandular  swellings  and  continued  fever.  The 
mortality  is  low. 

While  lesions  of  the  disease  may  be  found  in  the  spleen,  liver, 
lungs  and  lymph  glands,  a  number  of  squirrels  were  found  harbor- 
ing the  organism  in  a  single  bubo.     Such  animals  are  carriers  in 


ORGANISMS   PATHOGENIC   FOR   MAN   AND   ANIMALS  141 

the  same  sense  as  rodents  harboring  B.  pestis  in  residual  buboes. 
The  infection  has  also  been  found  in  jack  rabbits. 

Habitat  of  the  organism.  In  those  animals  which  may  be  classed 
as  carriers,  Bact.  tularense  is  harbored  in  one  or  more  buboes, 
the  inguinal,  pelvic,  axillary  and  cervical  glands  being  most 
frequently  affected.  McCoy  states  that  these  buboes  in  the 
squirrel  are  usually  as  large  as  a  pea,  sometimes  larger.  They  are 
rather  firm  and  when  cut  present  a  dry,  yellowish,  or  blood-stained 
surface.  Some  hemorrhage  is  frequently  found  in  the  surrounding 
tissue.  The  gland  structure  is,  as  a  rule,  replaced  by  a  firm,  caseous 
mass.     Purulent  glands  are  uncommon. 

Detection  and  management.  The  organism  can  be  definitely 
identified  in  affected  glands  through  bacteriological  means  and 
animal  inoculation  tests.  Bact.  tularense  is  a  very  difficult 
organism  to  cultivate,  the  conamon  types  of  media  being  unsuit- 
able for  its  growth.  McCoy  and  Chapin  found,  however,  that 
it  could  be  cultivated  on  an  egg  medium  made  entirely  of  the 
yolk.  The  organism  appears  as  a  minute  rod  0.3  to  0.7  micron 
in  length  and  is  frequently  capsulated.  It  stains  best  with  carbol- 
fuchsin  or  gentian  violet. 

Little  is  known  as  to  the  importance  of  Tularemia  in  squirrels 
or  rabbits  and  no  special  measures  have  been  employed  for  its 
control. 

11.  Bacillus  erysipelatis  suis 

Swine  erysipelas,  caused  by  Bacillus  erysipelatis  suis,  is  an 
important  disease  of  swine  in  European  countries.  Recently, 
however,  the  disease,  in  a  mild  form,  has  been  definitely  recog- 
nized in  the  United  States.  It  usually  manifests  itself  as  an  acute 
septicemia  with  a  characteristic  reddening  of  areas  of  the  skin.  A 
mild,  urticarial  form  ("diamond-skin  disease")  and  a  chronic 
type  are  also  recognized. 

The  carrier  problem  in  swine  erysipelas  has  been  given  con- 
siderable attention  by  European  investigators  and  the  fact 
definitely  established  that  a  large  percentage  of  hogs  in  localities 
where  the  disease  is  prevalent,  are  carriers  of  the  organism. 

Swine  erysipelas  occasionally  occurs  in  man  following  infec- 
tion of  skin  injuries.     In  such  cases  there  is  an  erysipelas-like 


142  CAERIERS   IN   INFECTIOUS   DISEASES 

reddening  of  the  skin  accompanied  by  a  swollen  condition  of  the 
neighboring  lymph  glands.  At  times,  the  sldn  lesions  assume  a 
blackish-red  color  and  cxfoUation  of  the  epidermis  occurs  with 
exudation  of  serum.  Swelling  of  joints  in  the  region  of  such  lesions 
may  also  be  noted.  Infection  through  ingestion  of  the  organism 
either  does  not  occur,  or  is  extremely  rare.  Lubowsky  (18)  re- 
ports a  case  of  jaundice  and  intestinal  catarrh  in  a  boy  in  whose 
feces  he  found  large  numbers  of  bacteria  identical  with  B.  ery- 
sipelatis  suis.  This  may  possibly  have  been  a  case  due  to  infection 
through  the  alimentary  tract  although  there  was  no  definite  proof 
of  same.  In  man  the  disease  usually  terminates  in  recovery  after 
3  or  4  weeks.     It  may,  however,  persist  for  two  or  three  months. 

Habitat  of  the  organism.  The  bacillus  of  swine  erysipelas  is 
frequently  found  in  large  numbers  in  the  crypts  of  the  tonsils  of 
carriers.  No  lesions  other  than  an  occasional  sUght  inflammatory 
process  have  been  noted  in  such  carriers. 

In  the  intestines  the  organism  is  very  frequently  found  in 
mucous  plugs  of  the  ileo-cecal  valve.  Olt  (19),  who  has  contrib- 
uted considerably  to  our  knowledge  of  carriers  in  swine  erysipe- 
las, frequently  noted  the  bacillus  in  minor  intestinal  lesions  caused 
originally  by  parasites,  especially  Strongyli. 

Out  of  50  apparently  normal  animals  examined,  Pitt  (20)  found 
28  or  56  per  cent  harboring  the  erysipelas  organism  in  their  tonsils. 
In  an  examination  of  the  intestines  of  66  animals  he  found  Bacillus 
erysipelatis  suis  in  26  or  over  43  per  cent  of  those  examined. 

Detection  and  management.  Because  of  the  large  percentage 
of  carriers  in  districts  where  the  disease  exists  and  the  diSiculty 
which  is  experienced  in  obtaining  satisfactory  specimens  of 
tonsil  secretions  for  bacteriological  examination,  routine  examina- 
tions for  the  detection  of  carriers  is  ordinarily  impracticable  in 
such  localities.  In  special  cases,  however,  where  valuable  breed- 
ing animals  are  being  introduced  into  territory  free  of  swine 
erysipelas,  bacteriological  examinations  should  be  made  of  "swab- 
bings"  from  the  throats  of  such  animals  during  their  quarantine 
period. 

Examination  of  the  feces  can  be  carried  out  without  difficulty, 
and  in  some  cases  will  yield  positive  results  where  the  baciUus  is 
carried  in  the  intestinal  tract.    However,   as  the  organism  is 


ORGANISMS    PATHOGENIC    FOR   MAN   AND   ANIMALS  143 

eliminated  only  sporadically  from  the  intestines,  a  single  negative 
bacteriological  finding,  obviously,  would  not  indicate  that  the 
animal  was  not  a  carrier. 

The  problem  in  those  localities  where  the  disease  exists  resolves 
itself  into  one  of  immunizing  susceptible  animals.  Fortunately, 
good  results  can  be  obtained  through  vaccination  against  the 
disease.  The  method  of  Pasteur,  giving  two  injections,  twelve 
days  apart,  of  a  culture  which  has  been  attenuated  by  passage 
through  rabbits,  may  be  used,  or  the  method  of  Lorenz  and 
Leclainche,  in  which  immune  serum  and  virulent  culture  are 
administered  simultaneously  and  followed  in  12  days  by  an  injec- 
tion of  culture  alone,  may  be  employed. 

Cases  of  the  disease  in  man  have  been  confined  to  persons 
working  around  hogs  in  localities  where  swine  erysipelas  exists, 
and  then  only  after  minor  skin  injuries.  Possible  transmission  of 
the  disease  to  man  from  carriers  can,  therefore,  be  largely  con- 
trolled through  proper  attention  to  tissue  injuries. 

12.  Miscellaneous  facultative-pathogenic  bacteria 

In  addition  to  the  various  organisms  of  specific  diseases  already 
enumerated,  animals  are  known  to  harbor  in  their  upper  air 
passages,  intestines,  genital  tracts,  and  in  the  case  of  milch 
animals,  in  their  udders,  a  considerable  variety  of  pyogenic  and 
facultative-pathogenic  organisms.  Under  suitable  conditions,  in 
the  body  of  their  host,  or  in  other  animals  or  man  directly  or 
indirectly  infected  by  such  carriers,  these  bacteria  are  often  cap- 
able of  setting  up  various  pathological  processes.  Included  in 
this  category  are  various  types  of  streptococci,  staphylococci, 
virulent  strains  of  Bacillus  coH,  BaciUus  pyocyaneus,  BaciUus 
pyogenes,  BaciUus  botuhnus.  Bacillus  aerogenes  capsulatus,  etc. 

Habitat  of  the  organism.  Streptococci,  Staphylococcus  albus, 
aureus  and  citreus,  and  Bacillus  pyocyaneus  are  among  those 
organisms  frequently  found  in  the  upper  air  passages  of  horses, 
cattle,  sheep,  swine,  dogs,  cats,  etc. 

Bacillus  pyogenes,  an  organism  which,  under  favorable  condi- 
tions, is  occasionally  responsible  for  suppurative  processes  in  the 
lungs,  pleurae,  peritoneum,  etc.,  of  hogs,  arthritis  in  hogs  and 
cattle,  and  inflammatory  processes  of  the  udder  of  cows,  goats 


144  CARRIERS  IN  INFECTIOUS  DISEASES 

and  sheep,  is  frequently  found  in  large  numbers  in  the  grayish, 
mushy  plugs  in  the  crypts  of  tonsils  of  healthy  hogs. 

Of  the  large  variety  of  bacteria  found  in  the  intestines  of  horses, 
cattle,  sheep,  swine,  etc.,  which  have  not  been  previously  men- 
tioned, and  which  may  prove  pathogenic  under  particular  condi- 
tions, are  virulent  types  of  Bacillus  coli.  Bacillus  lactis  aerogenes, 
Bacillus  proteus  mirabihs.  Bacillus  pyocyaneus,  Bacillus  botu- 
linus  and  Bacillus  aerogenes  capsulatus. 

Virulent  strains  of  Bacillus  coli  communis.  Bacillus  lactis 
aerogenes,  Bacillus  proteus  mirabilis  and  Bacillus  pyocyaneus,  are 
frequently  found  as  factors  in  cases  of  so-called  "white  scours" 
of  sucklings,  especially  calves. 

Bacillus  botuUnus  is  occasionally  found  in  the  intestinal  tract 
of  normal  hogs.  Such  carriers  are  of  importance  because  of  the 
possible  contamination  of  foodstuffs  with  particles  of  fecal  matter 
from  hogs. 

Bacillus  aerogenes  capsulatus  is  frequently  found  in  the  intes- 
tinal tracts  of  healthy  herbivora.  This  organism  has  not  been 
incriminated  as  a  cause  of  natural  infection  in  animals,  but  is  of 
importance  as  a  factor  in  the  infection  of  extensive  wounds  in 
man,  especially  war  wounds. 

Besides  those  organisms  heretofore  referred  to  as  being  harbored 
in  the  udders  of  cows  and  goats.  Bacillus  pyogenes.  Bacillus 
phegmasis  uberis,  and  various  types  of  staphylococci,  have  been 
found  in  the  udders  of  apparently  healthy  animals.  These 
organisms  are  capable,  under  favorable  conditions  of  producing 
inflammatory  and  purulent  processes  in  the  udders  of  animals, 
and  under  certain  circumstances,  may  possibly  prove  pathogenic 
for  man. 

Detection  and  management.  The  organisms  referred  to  in  the 
foregoing  paragraphs  can  practically  all  be  readily  detected  in 
carriers  through  the  employment  of  bacteriological  methods 
usually  utihzed  for  the  identification  of  the  different  members  of 
this  group,  without  difficulty. 

Because  they  are  chiefly  facultative-pathogenic  organisms  and 
with  one  or  two  exceptions,  are  widely  distributed,  but  little 
attention  has  been  given  to  carriers  of  these  bacteria. 


ORGANISMS    PATHOGENIC    FOR   MAN   AND   ANIMALS  145 

B,    CARRIERS    OF   PROTOZOA 

1.  Leishmania  canis 

In  several  localities  where  infantile  Leishmaniasis,  a  tropical, 
febrile  splenomengaly,  or  kala-azar  of  young  children  is  prevalent, 
Leishmania  canis,  an  organism  indistinguishable  from  Leishmania 
infantum,  has  been  frequently  found  in  dogs.  There  are  also 
rare  instances  of  its  occurrence  in  cats.  Sergent,  Lombard  and 
Quihchina  (21)  found  Leishmania  in  the  bone  marrow  of  a  cat. 
The  organism  has  been  demonstrated  in  dogs  in  Tunis,  Algeria, 
Italy,  Sicily,  Spain,  Greece,  Malta  and  Transcaucasia.  The 
disease  in  canines  is  usually  of  a  very  benign  character  although 
some  animals  may  show  marked  disturbances  of  health  as  a  result 
of  the  infection.  Frequently,  however,  Leishmania  canis  is 
harbored  in  the  bodies  of  dogs  showing  no  appreciable  evidence 
of  disease  whatever. 

There  is  considerable  evidence  tending  to  show  that  the  parasite 
of  Leishmaniasis  can  be  transmitted  from  animal  to  animal  by 
fleas.  The  probabihty  therefore  exists  that  carriers  of  the  organ- 
ism among  dogs  may  prove  a  source  of  infection  for  man. 

Habitat  of  the  organism.  The  Leishmania  harbored  by  dogs 
may  be  found  in  the  endotheUal  cells  of  the  spleen  and  liver,  in  the 
myelocytes  and  rarely  in  the  leucocytes  of  the  peripheral  blood. 
In  such  cells  they  appear  as  numerous  oval  bodies  2  to  4  microns  in 
length  and  1.5  to  2  microns  broad.  Each  organism  contains  a 
large  nucleus  and  a  smaller  blepharoplast.  Stained  by  Giemsa's 
method  the  large  nucleus  appears  as  a  pale  red  body  whereas  the 
smaller  blepharoplast  stains  a  dark  violet. 

Detection  and  management.  Very  rarely  an  occasional  poly- 
morphonuclear or  mononuclear  leucocyte  of  the  peripheral  blood 
may  be  found  to  contain  the  parasite.  Thus,  in  some  few  instances, 
careful  examination  of  a  number  of  blood  preparations  may  prove 
successful  in  demonstrating  the  organism  in  carriers.  Negative 
findings,  however,  are  without  significance. 

Microscopic  examination  of  material  obtained  by  puncture  of 
the  spleen  or  hver  is  the  only  method  giving  promise  of  success  in 
the  majority  of  cases  of  actual  carriers  of  Leishmania.  In  making 
the  puncture,  a  fine,  scrupulously  clean,  hypodermic  needle  attached 


146  CARRIERS  IN   INFECTIOUS  DISEASES 

to  a  syringe  by  means  of  a  small  piece  of  rubber  tubing,  is  em- 
ployed. It  is  important  that  the  needle  be  absolutely  dry  as  a 
trace  of  water  will  distort  or  burst  the  parasite,  making  its  rec- 
ognition exceedingly  difficult  or  impossible. 

In  the  dog  the  dorsal  end  of  the  spleen  does  not  vary  in  position. 
The  position  of  the  rest  of  the  organ,  however,  is  very  variable. 
The  dorsal  portion  of  the  spleen  Hes  ventral  to  the  vertebral  end 
of  the  last  rib  and  the  first  lumbar  transverse  process,  on  the  left 
side  of  the  body.  The  preferable  point  of  penetration,  therefore, 
is  just  posterior  to  the  last  rib  close  to  the  transverse  process  of 
the  first  lumbar  vertebrae.  In  making  a  liver  puncture  a  point 
close  to  the  anterior  border  of  the  right  twelfth  rib,  about  two- 
thirds  of  the  distance  between  the  vertebral  extremity  and  costo- 
chondral  junction  of  this  rib,  is  the  best  point  of  entry  for  the 
needle.  When  the  puncture  is  made  the  animal  should  be  well 
restrained  in  order  to  guard  against  tearing  the  organ  through 
sudden  movement. 

It  is  not  necessary  to  obtain  blood  from  the  organ  to  insure 
results,  a  small  amount  of  the  spleen  or  liver  pulp  being  most 
desirable.  On  withdrawing  the  needle  the  material  is  blown  out 
on  a  clean  cover  slip,  allowed  to  dry,  stained  by  Giemsa's  or 
Leishman's  methods,  and  examined  microscopically  for  Leish- 
mania. 

Until  recently,  medical  treatment  of  Leishmaniasis  offered  but 
Httle  hope  of  success.  Lately,  however,  in  human  medicine,  good 
results  have  been  obtained  from  intravenous  injections  of  tartar 
emetic,  extending  the  treatment  over  a  period  of  several  months, 
gradually  increasing  the  dosage.  While  in  exceptional  cases 
attempts  to  rid  dogs  of  the  parasite  by  medicinal  means  might  be 
justified,  generally,  animals  proven  to  be  carriers  of  Leishmania 
should  be  promptly  destroyed. 

As  fleas  are  Hkely  factors  in  the  transmission  of  the  infection, 
dogs  and  cats  in  localities  where  the  disease  is  prevalent  should  be 
kept  as  free  as  possible  from  fleas. 


ORGANISMS   PATHOGENIC   FOR  MAN  AND  ANIMALS  147 

C.    CARRIERS   OF   FILTERABLE   VIRUSES 

1.  The  virus  of  foot-and-mouth  disease 

Foot-and-mouth  disease  or  aphthous  fever,  caused  by  an  ultra- 
microscopic,  filterable  virus,  which  up  to  the  present  time  has  not 
been  artificially  cultivated,  is  an  important  disease  of  cattle  and 
other  cloven-footed  animals.  The  disease  is  prevalent  in  Europe, 
Asia,  Africa  and  South  America.  At  present  it  does  not  exist  in 
the  United  States,  the  last  and  largest  outbreak  having  occurred 
here  in  1914-1915. 

Loeffler,  Hess,  Zschokke,  Bartolucci,  Neverman  and  various 
other  investigators  have  shown  that  cattle  which  have  had  foot- 
and-mouth  disease  often  harbor  the  virus  and  are  capable  of  in- 
fecting other  animals  for  considerable  periods  following  recovery. 
Just  how  long  such  animals  may  remain  carriers  has  not  been 
definitely  ascertained.  Cases  are  on  record,  however,  in  which 
it  has  been  definitely  demonstrated  that  some  carriers  are  capable 
of  spreading  the  infection  7  months  after  recovery  from  the 
disease. 

Man  not  infrequently  contracts  foot-and-mouth  disease.  The 
infection  is  usually  brought  about  through  the  ingestion  of  raw 
milk  or  cheese  and  butter  prepared  from  milk  containing  the 
virus.  Infrequently  infection  may  occur  as  a  result  of  direct 
contact  with  affected  animals. 

The  disease  in  man  commences  with  a  sHght  fever,  with  nausea 
in  some  cases.  The  buccal  mucous  membranes  become  inflamed 
and  vesicles,  sometimes  as  large  as  peas,  develop,  especially  on 
the  lips,  gums  and  cheeks.  Vesicles  may  occasionally  develop 
on  the  conjunctivae.  Exanthema  of  the  skin  of  the  hands,  par- 
ticularly at  the  end  of  the  fingers  and  at  the  base  of  the  nails, 
occurs.  Headaches,  dullness,  dizziness,  abdominal  cramps  and 
diarrhea  may  be  observed.  The  disease  in  adults  usually  runs  a 
mild  course.  In  children  a  severe  gastro-intestinal  catarrah  is 
occasionally  associated  with  the  disease  and  may  lead  to  fatal 
terminations. 

Bussenius  and  Siegel  (22)  in  recording  16  outbreaks  of  foot-and- 
mouth  disease  among  animals,  occurring  between  1878  and  1896, 
report  that  entire  families,  and  in  several  instances  the  great  per- 


148  CARRIERS   IN   INFECTIOUS   DISEASES 

centage  of  persons  in  certain  townships,  became  affected  with  the 
disease.     A  total  of  75  cases  terminated  fatally. 

Thus,  while  the  disease  may  be  transmitted  to  the  human 
species  from  animals  suffering  from  the  disease,  until  more  definite 
knowledge  is  gained  as  to  the  various  possible  locations  of  the 
virus  in  the  body  of  recovered  animals  which  harbor  the  same, 
it  will  be  impossible  to  state  just  how  much  of  a  menace  carriers 
are  to  the  health  of  man. 

Habitat  of  the  virus.  As  above  indicated,  studies  of  the  carrier 
problem  in  foot-and-mouth  disease,  unfortunately,  have  not  as  yet 
estabhshed  with  certainty  all  possible  places  of  abode  of  the 
filterable  virus  in  the  animal  body. 

Zschokke  (23)  demonstrated  that  vesicles,  such  as  occur  in  the 
interdigital  space,  the  plantar  cushion  and  coronary  band,  may 
likewise  be  found  between  the  horn  and  sensitive  lamina  of  the 
hoof.  Such  vesicles  may  become  confluent  with  the  vesicles  of 
the  interdigital  space  or  plantar  cushion,  thus  opening  to  the  out- 
side, or  they  may  remain  separate.  In  the  latter  event  the  virus 
contained  in  the  vesicles  remains  in  such  location  long  after  the 
animal  has  recovered,  and  is  brought  to  the  surface  by  the  natural 
wearing  away  of  the  hoof.  The  spread  of  foot-and-mouth  disease 
by  a  carrier  thus  harboring  the  virus  in  the  hoof,  has  also  been 
reported  by  Bang  (24). 

It  does  not  follow,  of  course,  that  the  virus  of  foot-and-mouth 
disease  is  always  locahzed  in  the  hoofs  of  carriers.  That  it  is 
probably  harbored  in  other  parts  of  the  body  and  at  times  elimi- 
nated with  the  urine,  feces,  milk  or  saliva,  is  evident  from  the 
history  of  numerous  outbreaks  of  the  disease  following  the  intro- 
duction of  recovered  animals  into  herds  free  of  the  infection. 

Detection  and  management.  Loefller  (25) ,  in  concluding  his  report 
on  carriers  of  the  virus  of  foot-and-mouth  disease,  stated  that  at 
that  time  there  was  no  method  known  to  distinguish  virus  carriers. 
The  handicap  resulting  from  inability  to  utilize  bacteriological 
methods  in  the  study  of  such  carriers  is,  of  course,  obvious. 

During  the  1914-1915  outbreak  of  aphthous  fever  in  the  United 
States,  the  Bureau  of  Animal  Industry  of  the  United  States 
Department  of  Agriculture  (26)  before  releasing  from  quarantine 
the  National  Dairy  Show  Herd,  the  only  herd  of  cattle  affected 


ORGANISMS   PATHOGENIC    FOR   MAN   AND   ANIMALS  149 

with  the  disease  which  was  not  destroyed,  was  confronted  with 
the  problem  of  definitely  ascertaining  whether  or  not  any  of  these 
recovered  animals  were  carriers  of  the  virus.  The  disease  had 
been  eradicated  from  this  country  and  a  single  carrier  could,  of 
course,  have  started  the  infection  anew. 

The  recovered  animals  were  maintained  under  the  most  rigid 
type  of  quarantine.  A  number  of  healthy  young  cattle,  ranging 
from  one  to  one  and  one-half  years  of  age,  were  placed  in  contact 
with  the  recovered  animals  and  were  further  subjected  to  various 
inoculation  tests.  In  the  exposure  tests  a  susceptible  animal 
was  placed  between  two  recovered  animals  and  allowed  to  remain 
there  forty-eight  to  sixty-four  hours,  after  which  time  it  was 
placed  between  two  other  recovered  animals.  This  procedure 
was  carried  out  until  all  recovered  animals  had  been  given  an 
opportunity  to  infect  the  susceptible  animals.  The  susceptible 
animals  were  rotated  in  this  way  three  times  so  that  each  test  ani- 
mal was  exposed  at  least  one  hundred  and  forty-four  hours  to  each 
recovered  case.  In  the  meantime  the  recovered  animals  had  been 
divided  into  groups  and  specimens  of  saliva,  urine,  vaginal  dis- 
charge, watery  extract  of  feces,  scrapings  from  the  interdigital 
spaces,  and  milk  from  each  group  were  inoculated  into  the  buccal 
cavity  of  the  susceptible  animals  by  rubbing  the  membranes 
briskly  with  a  piece  of  gauze  saturated  with  such  specimens. 
Further,  towards  the  end  of  the  quarantine  period  a  number  of 
hogs  were  allowed  to  consume  such  leavings  and  droppings  from 
the  recovered  cattle  as  had  been  permitted  to  remain,  and  were  also 
fed  milk  from  the  cows. 

These  tests  were  continued  over  a  period  of  seven  months  when 
the  quarantine  was  Hfted.  They  indicated  that  there  were  no 
carriers,  capable  of  transmitting  the  disease,  in  this  particular 
herd  of  recovered  animals,  which  finding  was  subconsequentially 
borne  out  through  failure  of  the  released  animals  to  infect  others. 

Numerous  inoculation  and  exposure  tests,  as  above  outhned, 
to  determine  whether  or  not  animals  are  carriers  of  the  virus  of 
foot-and-mouth  disease,  obviously,  would  not  be  practicable  with 
individual  animals,  except  in  cases  of  breeding  stock  of  consider- 
able value. 


150  CARRIERS   IN   INFECTIOUS   DISEASES 

As  previously  indicated,  foot-and-mouth  disease  does  not  now 
exist  in  the  United  States  and  in  the  outbreaks  that  have  occurred 
all  infected  herds,  with  the  exception  of  the  single  instance  noted, 
were  promptly  destroyed.  Thus,  in  this  country  we  have  no 
carrier  problem.  However,  in  those  localities  where  the  disease 
exists,  sanitary  and  quarantine  measures  must  be  rehed  on  to 
minimize  the  spread  of  the  infection  by  carriers. 

With  a  view  to  eliminating  all  possibility  of  tranmission  of  the 
disease  to  man,  through  milk  from  cows  which  have  recovered 
from  the  disease,  the  same  should  be  properly  pasteurized. 


CHAPTER  XVIII 

Carriers  of  Organisms  Pathogenic  for  Animals  and 
Possibly  for  Man 

a.  carriers  of  bacteria 

1 .  Streptococcus  of  infectious  mastitis  of  cattle 

Milch  cows  frequently  suffer  from  mastitis  as  a  result  of  in- 
fection with  any  one  of  a  variety  of  bacteria.  A  streptococcus  of 
the  pyogenes  type,  however,  is  generally  responsible  for  that  form 
of  the  disease  which  is  transmitted  from  animal  to  animal.  Kitt, 
describing  a  streptococcus  of  bovine  mastitis,  referred  to  it  as 
"Streptococcus  agalactiae." 

Cows  which  have  apparently  recovered  from  mastitis,  and  in 
some  instances,  cows  with  no  history  of  having  had  the  disease, 
often  harbor  streptococci  in  their  udders  for  long  periods  of  time. 

Habitat  of  the  organism.  The  udder  may  harbor  and  eUminate 
streptococci  for  several  years.  In  those  cases  which  have  ap- 
parently not  suffered  an  attack  of  mastitis,  autopsy,  as  a  rule, 
reveals  no  demonstrable  changes  in  the  udder  tissue  except,  occa- 
sionally, a  shght  catarrhal  thickening  of  the  epitheUum  of  the  milk 
ducts.  In  cases  with  a  history  of  having  had  the  disease,  however, 
remaining  evidence  of  the  attack  is  usually  present  in  the  form  of 
jBbrous  tissue  changes  of  varying  degree,  with  atrophy  of  the 
alveolar  structure  of  the  parenchyma  of  the  udder.  A  thickened 
condition  of  the  epitheUal  Hning  of  the  milk  ducts,  from  which 
the  streptococcus  may  usually  be  isolated,  is  also  a  common 
finding  in  such  carriers. 

There  has  been  considerable  disagreement  among  various  in- 
vestigators as  to  the  pathogenicity  of  streptococci  of  bovine  origin 
for  man.  Some  are  of  the  opinion  that  man  is  readily  susceptible 
to  infection  with  bovine  streptococci  transmitted  through  milk 
from  infected  animals.  The  weight  of  evidence,  however,  stands 
in  refutation  of  such  conclusion.     Generally,  man  possesses  con- 

151 


152  CARRIERS   IN   INFECTIOUS   DISEASES 

siderable  immunity  to  streptococci  of  bovine  origin.  Undoubt- 
edly, however,  streptococci  of  human  origin  occasionally  gain  en- 
trance into  the  udder  of  cows  through  infected  milkers,  multiply 
in  the  glands,  and  may  or  may  not  set  up  pathological  processes. 
Milk  containing  such  organisms,  is  obviously  dangerous  as  food 
for  man  unless  pasteurized. 

Detection  and  management.  The  organism  can  usually  be  iso- 
lated from  the  milk  of  carriers,  by  ordinary  bacteriological 
methods,  without  difficulty.  After  the  udder  has  been  thoroughly 
washed  with  soap  and  water,  followed  by  a  1:1000  solution  of 
bichloride  of  mercury,  and  the  operator's  hands  disinfected,  the 
specimen  of  milk  should  be  drawn  direct  into  sterile  containers 
and  cultured  with  the  least  practical  delay,  icing  the  specimen  if 
there  will  be  appreciable  loss  of  time  in  getting  the  same  to  the 
laboratory. 

Our  lack  of  accurate  means  for  the  definite  identification  of 
different  types  of  streptococci  appKes,  of  course,  in  the  case  of  the 
organism  occurring  in  mastitis.  The  mastitis  streptococcus  must, 
however,  be  differentiated  from  Streptococcus  lactis  found  nor- 
mally in  milk.  Streptococcus  lactis  is  characterized  by  its  short 
chains  of  3  or  4  organisms,  some  cells  appearing  elongated  with 
tapering  ends.  When  grown  in  htmus  milk  the  color  reduction 
precedes  curdling  and  is  complete.  The  mastitis  streptococcus 
grows  in  long  chains,  and  in  litmus  milk,  causes  curdling  which 
may  be  followed  by  an  incomplete  reduction  of  the  Utmus. 

The  streptococcus  usually  enters  the  udder  through  the  milk 
ducts,  thus  the  transmission  of  the  infection  from  the  carrier  to 
healthy  cows  is  accomplished  chiefly  by  the  hands  of  the  milker. 
Spread  of  the  disease  by  this  means  can  be  controlled  by  requiring 
the  milker  to  disinfect  his  hands  after  milking  a  known  or  sus- 
pected carrier. 

Attempts  have  been  made  to  eliminate  the  streptococcus  from 
the  udders  of  carriers  through  the  injection  of  mild  antiseptic 
solutions  (10  per  cent  solution  of  argyrol,  etc.)  but  the  results, 
while  worthy  of  trial,  are  not  uniformly  successful.  Autogenous 
bacterins  have  also  been  employed  with  variable  results. 

A  number  of  carriers  of  the  organism  suffer  recurrences  of  the 
disease.     Such  cows  usually  develop  marked  udder  changes  with 


ORGANISMS   PATHOGENIC    FOR    ANIMALS   AND    MAN  153 

great  impairment  of  the  functional  activity  of  the  gland.  Thus, 
in  addition  to  being  carriers  of  the  infection,  they  are  a  loss  as 
milch  cows,  and  unless  they  have  a  distinct  breeding  value,  should 
be  "beefed."  Milk  from  herds  in  which  there  are  known  carriers 
of  streptococci  capable  of  producing  mastitis  in  cows,  should  be 
pasteurized,  in  order  to  eliminate  all  chance  of  it  proving  detri- 
mental to  the  health  of  man. 

2.  Bacterium  abortus  (Bang) 

Of  all  infectious  diseases  of  animals,  bovine  infectious  abortion, 
caused  by  Bacterium  abortus  (Bang),  is  probably  without  an  equal 
in  importance  from  the  standpoint  of  carriers.  When  it  is 
realized  that  from  an  economic  standpoint  infectious  abortion  of 
cattle  in  the  United  States  is  second  only  to  tuberculosis,  and  that 
carriers  are  very  potent  factors  in  its  spread,  their  importance 
cannot  be  over-rated.  According  to  Schroeder  (27)  60  per  cent 
of  all  infected  cows  at  some  time  harbor  Bacterium  abortus  in 
their  udders. 

While  up  to  the  present  time  this  organism  has  never  been 
definitely  demonstrated  to  be  pathogenic  for  man,  nevertheless, 
it  is  possible  that  in  specific  instances  and  under  certain  conditions, 
this  bacterium  which  is  capable  of  producing  marked  lesions  of  a 
grave  nature  in  various  experimental  animals,  may  prove  det- 
rimental to  human  beings  consuming  milk  from  carriers  of  the 
organism. 

Mohler  and  Traum  (28)  inoculated  emulsions  of  56  tonsils  and 
adenoids  from  children  into  guinea  pigs  and  produced  lesions  in 
the  liver,  spleen  and  testicles  in  one  of  the  inoculated  pigs.  Bac- 
terium abortus  was  recovered  from  these  lesions.  Larsen  and 
Sedgwick  (29)  submitted  blood  specimens  from  425  children  to 
the  complement-fixation  test  for  Bacterium  abortus  infection  and 
obtained  73  positive  reactions.  Later  work  by  these  investigators 
with  blood  serum  from  42  new-born  babies  who  had  not  received 
cows'  milk  resulted  in  negative  reaction  to  the  serological  test. 
Larsen  and  Sedgwick  indicated  that  these  reactions  might  possibly 
be  due  to  a  passive  immunity  resulting  from  the  ingestion  of  milk 
containing  antibodies.     Later  work  along  this  Hne  by  Cooledge 


154  CARRIERS   IN   INFECTIOUS   DISEASES 

(30)  tends  to  indicate  that  these  reactions  are  generally  due  to  the 
absorption  of  antibodies  contained  in  infected  milk. 

Habitat  of  the  organism.  Bacterium  abortus  has  a  particular 
affinity  for  embryonic  tissue,  its  natural  habitat  being  the  epithe- 
lium of  the  chorion.  In  infected  cows  it  is  practically  always 
found  in  the  uterus  during  pregnancy,  even  though  the  animal 
goes  through  the  full  period  of  gestation  and  has  an  apparently 
normal  parturition.  After  parturition,  however,  the  organism 
soon  disappears  from  the  uterus;  usually  within  several  weeks. 
In  exceptional  cases  it  may  persist  for  one  and  one-haK  to  two 
months. 

In  the  absence  of  embryonic  tissue  Bacterium  abortus  finds  the 
udder  a  suitable  place  to  maintain  its  existence.  Thus  in  a  large 
percentage  of  infected  cows  the  abortion  organism  is  harbored 
in  one  or  more  quarters  of  the  udder  and  may  be  ehminated  with 
the  milk  for  periods  varying  from  a  few  weeks  to  six  or  seven  years. 
Up  to  the  present  time  it  has  not  been  established  that  udder 
lesions,  definitely  attributable  to  Bacterium  abortus,  occur  in 
cows  carrying  the  organism. 

The  organism  remains  localized  in  the  udder  during  the  non- 
pregnant state  in  the  cow  but  readily  invades  the  uterus  through 
the  blood  stream  during  pregnancy.  Thus,  the  udder,  in  addition 
to  eliminating  the  infection  to  the  outside  more  or  less  continu- 
ously, constitutes  a  focal  source  of  infection  from  which  the  uterus 
of  its  host  may  be  reinfected  when  conditions  there  are  favorable. 

In  addition  to  the  cow,  the  bull  may  harbor  and  eliminate 
Bacterium  abortus  with  his  seminal  fluid.  Buck,  Creech  and 
Ladson  (31)  in  an  examination  of  325  mature  bulls,  isolated 
Bacterium  abortus  from  the  vesiculae  seminaHs  in  four  instances. 
The  organism  in  the  bull  apparently  shows  predilection  for  the 
seminal  vesicles  although  it  has  been  found  in  other  parts  of  the 
reproductive  organs. 

Detection  and  management.  In  the  detection  of  carriers  of 
Bacterium  abortus  among  cows  and  bulls,  the  agglutination  or 
complement-fixation  test  should  be  resorted  to,  and  this  followed, 
in  the  case  of  cows,  by  bacteriological  examinations  of  the  milk 
from  each  quarter  of  the  udder.  In  bulls,  when  practicable  to 
obtain  specimens  of  the  seminal  fluid,  the  same  should  Hkewise  be 


ORGANISMS   PATHOGENIC    FOR   ANIMALS   AND   MAN  155 

subjected  to  bacteriological  examination.  Because  of  its  relative 
simplicity,  the  agglutination  test  is  the  preferable  of  the  serological 
tests.  In  reliability  for  this  work,  it  compares  favorably  with  the 
complement-fixation  test. 

In  applying  the  agglutination  test  either  blood  or  milk  serum 
from  the  suspected  animal  may  be  used.  Blood  serum,  however, 
is  preferable  because  in  positive  cases  it  usually  possesses  a  greater 
number  of  agglutinins.  In  interpreting  the  agglutination  test 
the  lowest  dilution  in  which  agglutination  is  obtained  which  should 
be  considered  positive,  has  not  been  definitely  settled.  Agglutina- 
tion in  a  dilution  of  1  to  50  or  greater,  however,  should  be  taken 
to  indicate  that  the  animal  is  then,  or  was  at  some  time  previously, 
infected  with  Bacterium  abortus.  If  positive  reactions  are  ob- 
tained with  serum  in  dilutions  of  1  to  50  or  greater  but  in  less  than 
1:200,  the  animals  should  be  isolated  and  the  agglutination  test 
repeated  after  three  week  intervals.  Declining  reactions  in  di- 
lutions below  1:200  can  be  taken,  with  a  reasonable  degree  of 
certainty,  to  indicate  that  the  animal  is  not  a  disseminator  of 
Bacterium  abortus.  Schroeder  (27)  in  speaking  of  the  work  of 
the  United  States  Bureau  of  Animal  Industry  and  other  investi- 
gators with  the  agglutination  test  for  infectious  abortion,  states 
that  where  it  can  be  proven  that  a  cow  harbors  Bacterium  abortus 
in  her  udder,  the  agglutination  reaction  obtained  with  blood  or 
milk  serum  will  be  positive  in  a  dilution  of  1 :200  or  more. 

In  the  bacteriological  examination  of  milk  to  detect  carriers  of 
Bacterium  abortus,  Huddleson  (32)  recommends  a  fiver  infusion 
agar,  prepared  without  excessive  heating  and  filtered  through 
glass  wool  rather  than  cotton  or  paper,  and  with  a  H-ion  concen- 
tration between  6.6  and  6.4.  One  part  of  a  saturated  aqueous  solu- 
tion of  gentian  violet  to  10,000  parts  of  this  medium  will  inhibit 
the  growth  of  a  large  percentage  of  organisms  other  than  Bacterium 
abortus.  The  inoculated  plates  should  be  incubated  at  37.5°C. 
in  air-tight  containers  in  which  approximately  10  per  cent  of  the 
air  has  been  replaced  by  CO2  gas,  an  increased  carbon  dioxide 
tension  being  essential  to  the  initial  growth  of  Bacterium  abortus. 

Cows  and  bulls  demonstrated  to  be  carriers  of  Bacterium  abortus 
should  not  be  introduced  into  uninfected  herds.  The  ideal  method 
of  control,  would,  of  course,  be  the  slaughter  of  all  cattle  reacting 


156  CARRIERS   IN   INFECTIOUS   DISEASES 

to  the  agglutination  test  followed  by  thorough  disinfection  of  the 
premises  and  subsequent  retests  of  remaining  animals.  In  herds 
of  pure-bred  animals,  or  where  the  infection  is  hmited  and  of 
recent  introduction,  such  method  might  be  most  economic. 

Wliilc  this  radical  method  might  prove  the  most  economic 
procedure  in  some  instances,  generally,  in  herds  where  the  disease 
is  well  established,  and  in  which  there  is  a  high  percentage  of 
carriers,  it  would  not  be  feasible.  The  situation  in  such  cases 
can  probably  best  be  handled  by  maintaining  the  herd  intact 
without  introducing  new  animals  into  it  and  without  per- 
mitting animals  from  it  to  be  introduced  into  other  herds.  Thus, 
while  carriers  in  such  herds  will  not  be  ehminated  they  are  among 
animals  which  have  developed  more  or  less  immunity  to  the 
infection  and  consequently  are  in  the  place  where  they  will  do  the 
least  harm,  especially  where  energetic  sanitary  measures  are 
employed  with  a  view  to  preventing  mass  infection. 

The  bull,  known  to  harbor  and  eliminate  Bacterium  abortus, 
under  average  conditions  apparently  does  not  infect  healthy  cows 
through  the  vagina.  Infection  from  such  animal  is  usually 
brought  about  through  the  ingestion  of  food  or  water  contami- 
nated with  semen  dripping  from  the  penis  of  the  bull  or  which  has 
escaped  from  the  vagina  of  the  cow  subsequent  to  service.  Thus 
where  such  carriers  are  utilized  for  breeding  purposes,  precautions 
should  be  taken  to  prevent  the  spread  of  the  infection  in  this 
manner.  On  the  other  hand,  it  appears  possible  that  under  certain 
unusual  conditions,  especially  in  cases  of  shght  injury  occurring 
during  service,  cows  may  become  infected  through  the  vagina 
when  served  by  bulls  known  to  carry  and  eliminate  the  organism. 
It  cannot,  therefore,  be  definitely  stated  that  such  carriers  are 
invariably  safe  for  breeding  purposes. 

Although  possible  pathogenicity  of  Bacterium  abortus  for  man 
has  not  been  estabhshed,  pasteurization  of  milk  from  herds  in 
which  there  are  carriers  is  fully  warranted. 

B.    CARRIERS   OF   PROTOZOA 

1.  Trypanosomes 

There  are  several  important  diseases  of  domestic  animals, 
known  to  be  due  to  trypanosomes.     Further,  a  very  large  variety 


ORGANISMS   PATHOGENIC    FOR   ANIMALS   AND   MAN  157 

of  trypanosomes  of  little  or  no  established  pathogenicity  have 
been  noted  in  numerous  species  of  lower  animals. 

Of  the  more  important  diseases  of  animals  due  to  trypanosomes 
there  are  four  which  are  outstanding.  Nagana,  an  acute  or 
chronic  affection  of  solipeds,  cattle,  sheep,  goats  and  other 
ruminants,  caused  by  Trypanosoma  Brucei,  at  present  exists  in 
Southeast  Africa.  The  disease  is  characterized  by  remittent  fever, 
subcutaneous  edema,  marked  anemia  and  emaciation.  It  is 
transmitted  by  the  tsetse  fly. 

Surra,  designates  those  trypanosomiases  of  domestic  animals 
caused  by  Trypanosoma  Evansi.  The  disease  causes  great  losses 
among  sohpeds  and  camels.  Cattle  and  dogs  are  less  severely 
affected.  Surra  occurs  in  India,  Persia,  China,  the  Philippines, 
Sumatra,  Java,  Mauritius,  and  apparently  in  northeastern  Africa. 
Its  manifestations  are  in  a  general  way  similar  to  those  of  nagana. 
Tropical  flies,  especially  Tabanus  tropicus  and  Tabanus  lineola, 
are  transmitting  agents  of  the  disease. 

Dourine,  caused  by  Trypanosoma  equiperdum,  is  a  chronic 
disease  of  horses,  characterized  by  inflammatory  swelling  of  the 
external  genitals  wn'th  subsequent  symptoms  of  paralysis.  The 
disease  at  present  appears  to  exist  in  Spain,  Russia,  Africa,  Persia, 
India,  Java,  Roumania,  France  and  in  several  states  in  the  United 
States.  Characteristic  of  dourine  is  the  fact  that  the  natural 
mode  of  infection  is  through  coitus. 

Mai  de  caderas,  caused  by  Trypanosoma  equinum,  is  a  fatal 
subacute  or  chronic  disease  of  horses  in  South  America,  charac- 
terized by  a  paralysis  of  the  hind  quarters.  Definite  information 
is  lacking  as  to  the  natural  mode  of  infection.  It  is  believed, 
however,  that  flies  are  capable  of  transmitting  the  disease. 

There  are  numerous  records  of  carriers  of  trypanosomes  patho- 
genic for  animals,  especially  Trypanosoma  Brucei  and  Evansi. 
According  to  Laveran  and  Mesnil  (33)  a  large  variety  of  species, 
particularly  wild  ruminants,  harbor  Trypanosoma  Brucei  in  their 
blood  without  suffering  inlpairment  of  health.  Hutyra  and  Marek 
(34)  report  buffaloes,  antelopes,  hyenas,  zebras  and  quaggas  as 
carriers  of  the  organism,  such  animals  themselves  being  refractory 
to  the  infection. 

In  surra  the  bovine  species  is  much  more  resistant  to  the  disease 
than  equines.     However,  cattle  and  zebus  in  localities  where  the 


158  CARRIERS   IN   INFECTIOUS   DISEASES 

disease  exists  are  very  frequently  carriers  of  the  trypanosome. 
Such  animals  may  harbor  the  organism  for  years  without  mani- 
festing disturbances  of  health.  Camels  which  have  recovered  from 
surra  frequently  harbor  Trypanosoma  Evansi  in  their  blood  for 
long  periods  of  time.  In  India  the  buffalo  has  been  demonstrated 
as  a  frequent  carrier  of  the  parasite.  Various  wild  animals  such 
as  foxes,  jackals,  hyenas,  etc.,  may  carry  the  organism. 

In  dourine  animals  which  have  made  an  apparent  recovery  may 
continue  to  harbor  the  parasite  in  their  bodies  for  a  considerable 
period  of  time  as  is  evidenced  by  relapses  which  frequently  occur 
in  such  animals. 

Nothing  definite  is  known  regarding  carriers  in  Mai  de  caderas. 
-"^It  has  not  been  definitely  estabUshed  that  trypanosomes  patho- 
genic for  man  are,  under  natural  conditions,  carried  by  lower 
animals.  However,  Trypanosoma  gambiense,  the  causative 
agent  of  so-called  "sleeping  sickness"  in  man  has  been  experi- 
mentally demonstrated  to  be  pathogenic  for  various  species  of 
animals,  horses,  cattle,  sheep,  monkeys,  dogs,  cats,  rats  and  mice 
having  been  successfully  infected. 

Bruce  (35)  and  his  co-workers  were  able  to  transmit  Trypano- 
soma gambiense  from  infected  monkeys  to  cattle  by  the  bite  of 
Glossina  palpalis.  They  expressed  the  opinion  that  cattle  may 
harbor  the  parasite.  Thomas  and  Brienl  (36)  inoculated  a  cow 
with  Trypanosoma  gambiense  and  noted  that  it  suffered  a  slight 
disturbance  of  health  but  soon  returned  to  normal.  More  than  a 
year  later  the  blood  of  this  animal  was  still  infectious  for  rats. 

Habitat  of  the  organism.  With  the  exception  of  Trypanosoma 
equiperdum,  the  trypanosomes  above  mentioned,  when  harbored 
by  animals,  are  present  more  or  less  intermittently  in  the  blood 
stream.  At  periods  they  undoubtedly  inhabit  various  tissues  and 
organs  when  they  cannot  be  demonstrated  in  the  circulating  blood. 

In  dourine  the  trypanosome  can,  only  in  the  rarest  instances,  be 
demonstrated  in  the  blood  of  animals  harboring  the  organism 
within  their  bodies.  Recurrence  of  symptoms  of  the  disease  and 
positive  serological  reactions  constitute  the  evidence  that  such 
animals  actually  harbor  the  infection. 

Detection  and  management.  Microscopic  examination  of  blood 
preparations  from  animals  suspected  of  harboring  trypanosomes 


ORGANISMS   PATHOGENIC   FOR   ANIMALS   AND   MAN  159 

may  be  resorted  to  with  successful  results  in  a  number  of  positive 
cases.  However,  such  examination  frequently  results  in  failure 
to  demonstrate  the  parasite.  Animal  inoculation  tests  often  give 
positive  results  where  the  microscopic  examination  fails. 

The  complement-fixation  test  has  proven  of  great  value  in  the 
detection  of  dourine  among  horses  in  the  United  States,  and  the 
same  test  can  be  used  to  good  advantage  in  the  detection  of  car- 
riers of  trypanosomes.  However,  the  complement-fixation  test 
will  not  differentiate  the  type  of  trypanosome,  the  phenomena 
being  a  group  reaction.  Thus,  while  carriers  may  be  detected  by 
the  serological  test,  identification  of  the  type  of  organism  har- 
bored can  only  be  accomphshed  where  it  is  possible  to  demon- 
strate and  definitely  recognize  the  particular  parasite  microscopi- 
cally, or  where  the  typical  disease  can  be  produced  as  a  result  of 
experimental  inoculation  of  susceptible  animals. 

When  carriers  of  pathogenic  trypanosomes  are  detected  in 
localities  where  trypanosomiasis  is  not  prevalent,  their  destruction 
should  be  accomphshed.  In  districts  where  the  disease  is  wide- 
spread, however,  measures  looking  to  the  protection  of  animals 
from  flies,  must  be  chiefly  reUed  upon  to  combat  the  carrier  prob- 
lem. In  cases  of  animals  harboring  the  dourine  trypanosome, 
the  problem  can  be  effectively  handled  by  castrating  stalhons 
known  to  harbor  the  organism  and  prohibiting  the  breeding  of 
infected  mares,  or  destroying  the  latter  in  countries  where  efforts 
are  being  made  to  eradicate  the  disease. 

2.  Other  'protozoal  and  metazoal  infections 

There  is  evidence  tending  to  indicate  that  different  species  of 
animals  may  occasionally  carry  in  their  intestinal  tracts  various 
rhizopoda,  ciliata,  flagellata  and  sporozoa,  in  small  numbers 
without  manifesting  disturbances  of  health.  Again,  it  is  possible 
that  certain  of  such  parasites  may  be  harbored  in  rather  large 
numbers  by  a  particular  species  without  detrimental  results, 
whereas  the  same  organism  gaining  entrance  into  the  body  of 
other  species,  including  man,  may  cause  marked  disturbances. 
At  the  present  time,  however,  there  is  very  little  known  regarding 
carriers  of  this  type. 


160  CARRIERS   IN   INFECTIOUS   DISEASES 

Eichhorn  and  Gallagher  (37),  in  reporting  an  outbreak  of  amebic 
dysentery  among  monkeys,  point  out  the  possibiHty  of  carriers 
occurring  among  such  animals.  The  parasite  in  the  cases  de- 
scribed, however,  apparently  was  not  Endameba  histolytica,  the 
causative  agent  of  amebic  dj^scntery  in  man. 

Adult  turkeys  may  harbor  in  their  intestines  Ameba  melea- 
gridis,  the  etiological  factor  in  infectious  enterohepatitis  ("Black- 
head") of  turkeys.  Apparently  this  parasite  is  also  carried  by 
chickens.  There  is  no  evidence  that  the  organism  is  pathogenic 
for  man. 

Balantidium  coli  is  commonly  found  in  the  lower  portion  of 
the  intestines  of  hogs.  It  is  usually  nonpathogenic  for  these 
animals  but  may  occasionally  produce  a  mild  form  of  dysentery. 
This  organism  is  capable  of  producing  dysentery  and  ulceration  of 
the  intestines  in  man,  occasionally  setting  up  a  process  which 
terminates  in  death. 

Several  types  of  trichomonas  occur  in  swine  and  fowls.  So 
far  as  is  known,  however,  they  are  of  but  little  importance. 

Various  coccidia  occur  in  cattle,  sheep,  dogs,  cats,  rabbits, 
fowls,  etc.  Undoubtedly  there  exists  among  such  animals  those 
which  could  be  properly  placed  in  the  category  of  carriers.  There 
is,  however,  but  little  information  available  on  the  subject.  There 
are  several  cases  on  record  where  man  has  been  infected  with 
Coccidium  cuniculi,  the  common  coccidium  of  rabbits. 

In  the  same  sense  that  carriers  of  protozoan  organisms  are 
recognized,  carriers  of  various  types  of  hehninths  exist  among 
animals.  Our  knowledge  of  this  phase  of  the  carrier  problem, 
however,  is  very  meagre. 


CHAPTER  XIX 

Carriers  of  Organisms  Pathogenic  for  Lower  Animals 
Only 

A.  carriers  of  bacteria 
1.  Bacillus  hipolaris  septicus 

Bacillus  bipolaris  septicus,  various  types  of  which  make  up  the 
"Hemorrhagic  Septicemia"  or  "Pasteurella"  group  and  are  known 
as  B.  bovisepticus,  B.  equisepticus,  B,  suisepticus,  B.  ovisepticus, 
B.  avisepticus,  etc.,  according  to  the  species  of  animal  from  which 
isolated,  is  frequently  harbored  in  the  bodies  of  normal  animals. 

According  to  Moore  (38),  upward  of  80  per  cent  of  normal  cattle 
harbor  in  their  upper  air  passages  organisms  corresponding  in 
cultural  characteristics,  and  in  their  effect  upon  rabbits,  to  Bacillus 
bipolaris  septicus.  Horses,  swine,  sheep,  dogs,  cats  and  fowls  have 
also  frequently  been  found  as  carriers  of  the  organism. 

Fortunately,  this  baciUus  is  usually  more  or  less  of  a  facultative- 
pathogenic  organism  and  only  produces  its  specific  disease  when 
the  normal  resistance  of  the  invaded  animal  is  lowered  or  following 
a  particular  increase  in  its  own  virulence  which  sometimes  occurs 
without  apparent  cause. 

Habitat  of  the  organism.  The  favorite  location  of  Bacillus 
bipolaris  septicus  in  carriers  apparently  is  the  epithelium  of  the 
nasal  cavity,  larynx,  pharynx  and  trachea.  It  is  also  found  rela- 
tively frequent  in  the  small  and  large  intestines. 

Manninger  (39)  cites  an  experiment  in  which  chickens  were  arti- 
ficially infected  with  the  fowl  cholera  organism  (B.  avisepticus) 
and,  while  not  developing  the  disease,  ehminated  the  organism 
through  their  kidneys  for  months.  He  also  cites  an  instance  of 
a  hen  harboring  highly  virulent  fowl  cholera  organisms  in  an  old 
encapsulated  abscess  in  the  region  of  a  joint  in  which  she  had  a 
chronic  arthritis. 

161 


162  CARRIERS   IN   INFECTIOUS   DISEASES 

No  tissue  alterations,  commonly  found,  and  definitely  attrib- 
utable to  this  organism  when  harbored  by  apparently  normal 
animals,  have  been  described. 

Detection  and  management.  The  organism  can,  as  a  rule,  be 
readily  cultivated  from  the  upper  air  passages  of  carriers  by  ordi- 
nary bacteriological  methods,  and  when  carried  in  the  intestinal 
tract,  may  likewise  be  isolated  from  the  feces,  but  with  less 
frequency. 

Because  of  the  high  percentage  of  carriers  and  the  widespread 
distribution  of  organism  of  the  Pasteurella  group  in  nature,  we 
are  without  means  for  ehminating  them.  Efforts,  therefore,  must 
be  directed  along  sanitary  lines  with  a  view  to  maintaining  the 
general  health  and  resistance  of  animals,  rather  than  endeavoring 
to  ehminate  the  carriers.  Further,  vaccination  against  infection 
with  organisms  of  this  group,  with  properly  prepared  vaccines,  is 
possibly  of  value. 

2.  Bacillus  necrophorus 

Bacillus  necrophorus  (Fliigge)  under  this  and  such  additional 
names  as  "Bacillus  diphtheriae  vitulorum"  (Loeffler),  "Bacillus 
fihformis"  (Schiitz),  "Actinomyces  cunicuh"  (Gasperini),  and 
"Streptothrix  necrophora"  (Kitt),  since  1884  has  been  recognized 
as  the  causative  factor  of  a  variety  of  important  pathological 
processes  in  domestic  animals.  The  organism  is  widely  distributed 
and  is  frequently  harbored  in  the  intestines  of  healthy  herbivorous 
animals,  especially  hogs.  There  is  no  record  of  its  having  proved 
pathogenic  for  man. 

The  principal  pathological  conditions  for  which  bacillus  necroph- 
orus is  responsible  includes  gangrenous  dermatitis  of  horses  and 
mules,  the  so-called  "foot-rot"  and  "Up-and-leg  ulceration"  of 
sheep,  necrotic  stomatitis  of  cattle,  and  multiple  necrotic  foci 
in  the  liver  of  cattle  and  hogs.  The  organism  is  also  found  as  a 
secondary  factor  in  various  other  diseases  and  conditions.  Its 
lesions  are  characterized  by  a  coagulation  necrosis  with  subsequent 
caseation. 

In  the  United  States  Army  during  the  world  war,  gangrenous 
dermatitis  of  horses  and  mules  proved  to  be  the  second  most 
important  disease  of  animals  in  the  United  States.     During  the 


ORGANISMS   PATHOGENIC   FOR   LOWER   ANIMALS    ONLY       163 

six  month  period  July  to  December,  1918,  4036  cases  of  the  disease 
were  reported.  Of  this  total  212  cases  died  or  had  to  be  destroyed 
on  account  of  the  disease.  Of  all  deaths,  from  all  causes,  among 
all  Army  animals  in  the  United  States,  for  this  period  6.41  per  cent 
were  due  to  gangrenous  dermatitis.  The  weekly  sick  report  during 
this  period  showed  a  ratio  of  over  275  animals  per  1000  on  sick 
report  as  a  result  of  Bacillus  necrophorus  infection. 

Where  a  considerable  number  of  animals  are  kept  together  in 
corrals,  pens,  lots,  etc.,  which  are  wet  and  muddy,  or  contain 
large  accumulations  of  manure,  the  infection  spreads  rapidly 
when  once  introduced.  The  importance  of  carriers  when  placed 
among  animals  in  such  surroundings  is  obvious. 

Habitat  of  the  organism.  Carriers  of  Bacillus  necrophorus 
harbor  the  organism  in  their  intestinal  tracts,  usually  without 
manifesting  appreciable  lesions  However,  in  hogs  which  have  had 
the  chronic  form  of  hog  cholera,  Bacillus  necrophorus  is  frequently 
found  associated  with  Bacillus  suipestifer  in  the  intestinal  ulcers 
described  in  the  discussion  of  carriers  of  the  Salmonella  group 
(page  131).  Further,  the  organism  may  be  found  in  minor 
intestinal  lesions  originally  due  to  parasites. 

Detection  and  management.  The  detection  of  Bacillus  necroph- 
orus in  carriers  by  bacteriological  methods  is  by  no  means  an 
easy  undertaking.  In  the  first  place,  carriers  of  this  bacillus  as  a 
rule  do  not  eliminate  it  in  large  numbers.  Further,  this  organism 
is  an  extremely  difficult  anaerobe  to  isolate  in  pure  culture.  Char- 
acteristic of  the  organism  is  its  beaded  appearance  in  stained  prep- 
arations. While  it  is  distinctly  a  pleomorphic  organism,  it  usually 
occurs  as  a  long  slender  rod  appearing  more  or  less  bent.  Long 
filaments,  measuring  in  some  instances,  over  100  microns  in  length, 
are  frequently  observed. 

The  subcutaneous  inoculation  of  rabbits  with  suspected  material 
gives  rise  in  positive  cases  to  a  hard  inflammatory  induration  at 
the  site  of  inoculation.  After  a  few  days  the  tissue  in  this  area 
becomes  caseous  and  necrotic,  the  rabbit  usually  dying  within  10 
or  12  days.  The  necrotic  tissue  gives  off  a  characteristic  cheesy 
odor.  In  such  lesions  B.  necrophorus  can  be  demonstrated  in 
large  numbers. 


164  CARRIERS  IN  INFECTIOUS  DISEASES 

Sanitary  measures  afford  the  chief  means  of  preventing  B. 
necrophorus  infections.  Well  drained  corrals,  pens,  etc.,  and 
proper  disposal  of  manure  and  litter  are  potent  factors  in  con- 
trolUng  the  infection. 

S.  Bacillus  paratuherculosis 

Paratuberculous  enteritis,  or  Johne's  Disease,  is  a  serious, 
chronic,  infectious  disease  of  the  bovine  species,  characterized  by 
a  marked  thickening  and  corrugation  of  the  mucous  membrane 
of  the  intestine.  The  etiological  factor.  Bacillus  paratuherculosis, 
is  an  acid-fast  organism  closely  resembhng  the  tubercle  bacillus. 

Young  cattle  are  more  resistant  to  the  infection  than  adults, 
yet  they  are  capable  of  carrying  the  infection  for  months  or  even 
several  years,  and  therefore  constitute  an  important  carrier  prob- 
lem. After  maturity,  a  large  percentage  of  such  carriers  them- 
selves become  affected  with  the  disease,  especially  following 
calving. 

While  the  disease  in  the  vast  number  of  cases  runs  a  long  chronic 
course  and  terminates  fatally,  there  are,  among  adult  cattle, 
occasionally  cases  of  apparent  recovery.  Such  animals  invariably 
are  active  carriers  of  the  infection,  in  some  instances  for  periods 
of  time  extending  over  a  number  of  months.  Usually,  however, 
they  suffer  recurrences  which  finally  result  in  death.  Such 
animals  must  be  differentiated  from  the  true  immune  carrier,  as 
generally  they  are,  in  a  strict  sense,  arrested  cases,  the  carrier 
state  existing  during  the  period  of  inactivity. 

Habitat  of  the  organism  Carriers  of  the  bacillus  of  paratuber- 
culous enteritis  harbor  the  organism  in  the  mucous  membrane 
of  the  small  and  large  intestine,  the  lower  portion  of  the  small 
intestine  being  a  favorite  location. 

In  the  case  of  young  cattle  which,  while  carrying  the  organism, 
have  not  suffered  an  attack  of  the  disease,  autopsy  reveals  little 
or  no  changes  in  the  intestinal  tract.  Occasionally,  however, 
small  areas  of  the  intestinal  mucous  membrane  may  appear 
thickened  and  slightly  rugous.  Sections  from  such  areas  show, 
principally,  cellular  infiltration  and  a  swollen  and  more  or  less 
distorted  condition  of  the  villi.  The  organism  can  readily  be 
demonstrated  in  such  lesions. 


ORGANISMS   PATHOGENIC    FOR   LOWER   ANIMALS   ONLY       165 

In  carriers  which  have  had  the  disease  the  mucous  membrane  of 
portions  of  the  intestines  appears,  as  a  rule,  greatly  thickened  and 
has  a  characteristic  convoluted  or  corrugated  appearance.  Micro- 
scopic examination  of  sections  of  such  tissue  reveals  a  cellular 
infiltration,  a  marked  distorted  condition  of  the  villi,  and  an 
increase  of  the  interstitial  tissue  between  the  tubular  glands  in  the 
glandular  layer,  with  atrophy  of  the  glands.  In  such  sections  the 
acid-fast  bacillus  can  usually  be  demonstrated  in  considerable 
numbers. 

Detection  and  management.  Microscopical  examination  of  the 
feces  from  actual  carriers  often  yield  negative  results.  Repeated 
examinations  of  considerable  quantities  of  the  feces  should,  there- 
fore, be  made.  Further,  the  bacillus  of  Johne's  disease  must  be 
differentiated  from  other  acid-fast  organisms.  As  it  is  non- 
pathogenic for  the  guinea  pig,  such  experimental  animal  can  be 
utihzed  in  differentiating  the  organism  from  the  tubercle  bacillus. 
It  must,  however,  still  be  differentiated  from  acid-fast  organisms 
of  a  saprophytic  nature.  As  it  is  exceedingly  difficult  to  cultivate 
the  Bacillus  paratuberculosis,  cultural  methods,  at  present,  offer 
but  little  aid.  Hastings,  Beach  and  Hadley  (40)  report  fairly 
good  results  with  a  medium  prepared  by  adding  to  filtered  broth 
cultures  of  the  human  tubercle  bacillus  sterihzed  in  the  Arnold 
sterilizer  for  two  hours,  15  grams  of  agar,  2  grams  of  beef  extract, 
5  grams  of  peptone,  2.5  grams  of  potassium  acid  phosphate  and 
24  cc.  of  glycerine,  per  liter  of  the  filtered  culture,  adjusting  the 
reaction  to  plus  1.5  to  phenolphthalein.  A  small  amount  of  sterile 
blood  serum  should  be  run  over  the  surface  of  this  medium  just 
before  inoculation. 

Bang  (41)  and  several  other  investigators  have  called  attention 
to  the  value  of  avian  tuberculin  for  the  diagnosis  of  paratuber- 
culous  enteritis.  Tuberculin  prepared  from  the  avian  type  of 
tubercle  bacillus  is  utihzed  in  order  to  ehminate  the  possibihty  of 
comphcations  arising  from  reactions  in  tuberculous  cows,  animals 
infected  with  the  bovine  or  human  type  of  tubercle  bacillus  not 
reacting  to  avian  tubercuhn.  Such  tuberculin  test  may  be  used 
in  the  detection  of  carriers. 

A  diagnostic  agent  ("Johnin")  prepared  similarly  to  tuberculin 
but  from  the  specific  organism  of  the  disease  has  been  made  and 


166  CARRIERS   IN   INFECTIOUS   DISEASES 

gives  satisfactory  results  in  diagnosing  the  infection.  However, 
because  of  the  difficulty  encountered  in  propagating  the  bacillus 
it  is  but  seldom  that  such  agent  can  be  obtained. 

As  Johne's  disease  is  fatal  in  the  large  percentage  of  cases,  and 
as  carriers,  as  a  rule,  eventually  develop  the  disease,  or  if  they 
have  already  had  it,  suffer  recurrences  which  finally  prove  fatal, 
they  should  be  slaughtered. 

4..  Bacterium  pullorum 

The  carrier  problem  in  bacillary  white  diarrhea  of  young  chicks, 
a  disease  due  to  an  organism  known  as  Bacterium  pullorum,  is 
without  doubt  the  most  important  problem  of  its  kind  in  the 
various  infectious  diseases  of  fowls.  Gage  (42),  Jones  (43), 
Rettger  (44),  and  various  other  investigators,  have  definitely 
shown  that  the  perpetuation  of  this  disease  is  due,  in  a  large 
measure,  to  carriers  of  the  organism  among  adult  hens,  who  may 
harbor  the  organism  throughout  their  Ufe. 

The  organism  is  apparently  non-pathogenic  for  man.  This  is  a 
fortunate  circumstance  in  view  of  the  fact  that  the  bacterium  is 
frequently  found  in  freshly  laid  eggs  of  carriers. 

Habitat  of  the  organism.  Carriers  of  Bacterium  pullorum  harbor 
the  same  in  their  ovaries.  The  changes  in  such  ovaries  are  usually 
well  marked.  Examination  of  a  normal  ovary  of  the  laying  hen 
demonstrates  a  large  mass  of  ova  in  various  stages  of  development, 
some  appearing  as  minute,  colorless  spheres,  just  visible  to  the 
naked  eye,  others  being  as  large  as  a  normal  yolk  and  of  a  rich 
yellow  color.  The  ovary  which  is  infected  with  Bacterium  pul- 
lorum, while  possessing  some  apparently  normal  ova  in  various 
stages  of  development,  will  usually  be  found  to  contain  a  number 
of  different  sizes  which  appear  as  cysts.  The  smaller  of  such 
ova  appear  round  or  are  shghtly  distorted.  The  larger  are  usually 
distorted  so  that  they  appear  angular  or  flattened,  and  are  of  a 
mottled  appearance,  some  lighter  than  normal,  others  of  a  dark, 
yellowish-brown  color.  In  some  cases  the  color  is  a  peculiar  dark- 
green,  suggesting  gangrene.  The  diseased  ova  contain  a  cheesy 
mass  out  of  which  may  be  expressed  a  clear  amber-colored  fluid. 
Bacterium  pullorum  may  be  readily  isolated  from  such  material. 


ORGANISMS    PATHOGENIC    FOR   LOWER   ANIMALS    ONLY       167 

A  large  percentage  of  ova  of  hens  with  such  ovaries  never 
mature.  However,  such  birds  frequently  lay  fully  developed  eggs, 
capable  of  hatching,  which  contain  the  organism.  In  such  cases 
the  resulting  chick  has  white  diarrhea  and  infects  others  in  the 
brood  which  may  have  been  hatched  from  healthy  eggs.  Of  those 
that  survive  a  large  percentage  of  the  females  are  carriers,  thus 
continuing  the  cycle  of  infection. 

Rettger,  Kirkpatrick  and  Jones  (44)  in  a  series  of  experiments 
which  they  conducted  found  that  over  25  per  cent  of  female  chicks 
infected  with  Bact.  pullorum  when  small  became  permanent 
carriers  of  the  infection. 

Detection  and  management.  Jones  (43)  found  that  the  macro- 
scopic agglutination  test  could  be  utilized  to  good  advantage  in 
detecting  hens  harboring  Bact.  pullorum  in  their  ovaries.  The 
value  of  this  test  has  been  confirmed  by  a  number  of  other  in- 
vestigators. 

In  carrying  out  the  agglutination  test  dilutions  of  1 :  50,  1 :  100 
and  1:200  are  made.  In  Jones'  work  serum  from  all  infected 
fowls  agglutinated  in  1:50  and  1:100  dilutions,  91  per  cent  agglu- 
tinated in  the  1 :200  dilutions  and  82  per  cent  of  1 :500.  Aggluti- 
nation in  dilutions  of  1 :  100  or  more  should  be  considered  positive, 
in  the  1:50  dilution,  suspicious. 

Hens  demonstrated  to  be  carriers  of  Bact.  pullorum  should  not 
be  kept  on  premises  where  chickens  are  raised.  Further,  because  of 
the  diseased  condition  of  the  ovaries,  such  birds  are  not  profitable 
layers.  Therefore,  their  slaughter  for  food  purposes  is  an  econom- 
ical procedure. 

B.    CARRIERS   OF   PROTOZOA 

1 .  Piroplasma  higeminum  and  Piroplasma  hovis 

In  the  southern  part  of  the  United  States  bovine  piroplasmosis 
or  Texas  fever  is  an  important  disease  of  cattle.  It  is  caused  by 
Piroplasma  bigeminum  and  is  commonly  transmitted  by  the  tick 
Margarapus  annulatus.  European  piroplasmosis  (British  "Red 
Water")  is  generally  due  to  a  smaller  type  of  organism,  Piroplasma 
bo  vis,  and  is  usually  transmitted  by  Ixodes  ricinus.  CHnically, 
Texas  fever  and  European  piroplasmosis  of  cattle  are  practically 


168  CARRIERS   IN   INFECTIOUS  DISEASES 

indistinguishable.  However,  cattle  immune  to  the  Texas  fever 
piroplasma  are  susceptible  to  the  European  type,  thus  clearly 
estabhshing  that  the  two  parasites  are  different  species. 

Young  cattle  are  quite  resistant  to  piroplasma  infection.  Ani- 
mals raised  in  infected  localities  usually  become  immunized  so  that 
they  do  not  suffer  from  severe  attacks  of  the  disease.  Such 
animals,  however,  harbor  the  piroplasma  and  if  introduced  into 
districts  where  piroplasmosis  does  not  exist,  prove  a  source  of 
infection  for  susceptible  cattle  if  transmitting  ticks  are  present, 

Piroplasma  may  persist  for  years  in  the  blood  of  immune  or 
recovered  animals.  Schroeder  and  Cotton  (45)  reported  the  case 
of  a  cow  whose  blood  was  infectious  for  over  10  years  subsequent 
to  her  arrival  at  the  United  States  Department  of  Agriculture 
Experiment  Station  from  a  Texas  fever  district  in  North  Carohna. 

Habitat  of  the  organism.  Carriers  of  Piroplasma  bigeminum  and 
Piroplasma  bovis  harbor  the  same  in  their  red  blood  corpuscles. 
Piroplasmosis  is  characterized  by  a  marked  diminution  of  red  cells. 
After  recovery,  however,  the  number  of  red  cells  gradually  ap- 
proach normal  so  that  in  carriers  blood  cell  counts  often  demon- 
strate Httle  or  no  diminution. 

Detection  and  management.  The  parasites  of  bovine  piroplas- 
mosis may  be  demonstrated  in  the  blood  of  carriers  by  micro- 
scopic examination.  They  are  present,  of  course,  in  smaller 
numbers  than  are  found  in  cases  of  the  disease,  consequently  a 
more  searching  examination  is  often  necessary. 

After  shaving  and  cleaning  an  area  of  the  ear  of  a  suspected 
carrier  a  drop  of  blood  should  be  obtained  by  making  a  small 
incision  with  a  scalpel  or  lancet.  A  blood  film  should  be  prepared 
on  a  clean  slide  and  stained  for  microscopic  examination  with 
Romanowski  stain  or  one  of  its  modifications.  Piroplasma  bigem- 
inum appear  as  pyriform  organisms  varying  from  2,0  to  4.0 
microns  in  length  and  1.5  to  2,0  microns  broad,  usually  occurring 
in  pairs  in  the  red  blood  cells.  They  may  be  found  side  by  side 
but  frequently  appear  end  to  end  on  a  parallel  fine  or  at  an  angle, 
the  pointed  ends  being  in  opposition  (dumb-bell  forms) ,  In  addi- 
tion to  the  pear-shaped  forms,  round,  oval  or  pyramidal  shapes 
may  be  noted.  Occasionally  but  one  parasite  may  be  found  in  a 
cell  while  in  other  cells  several  pairs  may  be  noted.     Piroplasma 


ORGANISMS   PATHOGENIC    FOR   LOWER   ANIMALS    ONLY       169 

bovis  differs  from  Piroplasma  bigeminum  in  that  it  is  smaller  and 
does  not  have  the  tendency  to  occur  in  distinct  pear-shaped  forms. 

As  bovine  piroplasmosis  is  transmitted  from  animal  to  animal 
by  certain  species  of  ticks,  preventative  measures,  in  the  United 
States,  have  been  reduced  to  quarantine  of  areas  infected  with  the 
cattle  tick  and  the  inauguration  of  a  well-organized  campaign  of 
tick  eradication.  Cattle  from  such  districts  cannot  be  shipped 
into  uninfected  territory  except  under  certain  restricted  condi- 
tions. Between  1906  (the  year  eradication  of  the  cattle  tick  was 
undertaken)  and  December  1921,  523,837  square  miles  of  infected 
territory  in  the  United  States  were  freed  of  cattle  ticks  through 
systematic  dipping  of  the  cattle,  reducing  the  infected  area  to 
206,015  square  miles. 

In  locahties  where  bovine  piroplasmosis  is  more  or  less  wide- 
spread, and  where  quarantine  and  measures  for  the  eradication  of 
transmitting  ticks  are  not  employed,  the  immunization  of  sus- 
ceptible animals  constitutes  the  only  means  of  protecting  cattle 
from  infection  coming  from  carriers.  This  is  accomplished  natu- 
rall}"  in  young  animals  brought  up  in  infected  districts.  Suscep- 
tible adults  may  be  immunized  through  the  subcutaneous  injec- 
tion of  small  amounts  (5  cc.)  of  defibrinated  blood  of  immunized 
or  recovered  cattle,  preferably  calves,  in  which  the  parasite  occurs 
in  small  numbers.  The  inoculated  animals  should  be  kept  in  the 
stable  for  three  or  four  weeks  before  being  turned  out  to  pasture. 
Eight  to  ten  days  after  the  inoculation  the  animals  manifest 
symptoms  of  the  disease  which  usually  last  from  one  to  two  weeks. 
Pregnant  cows  and  animals  in  a  state  of  impaired  health  should 
not  be  inoculated. 

Most  inoculated  animals  survive  the  infection,  although  oc- 
casionally a  few  are  lost.  However,  as  the  percentage  of  losses 
among  non-inoculated  animals,  in  localities  where  the  disease  is 
wide-spread,  is  considerably  greater  than  that  occurring  in  arti- 
ficially infected  animals,  the  inoculation  procedure  is  warranted. 

Where  vaccination  is  employed  to  immunize  susceptible  ani- 
mals, we  have,  so  far  as  the  carrier  problem  goes,  a  unique  situa- 
tion. The  method  employed  to  protect  non-immunes  against 
infection  actually  produces  a  large  number  of  carriers. 


170  CARRIERS  IN   INFECTIOUS  DISEASES 

3.  Piroplasma  cahalli  and  Nuttallia  equi 

Prior  to  1910,  Piroplasma  caballi,  Piroplasma  equi  or  Babesia 
equi,  as  it  has  been  variously  termed,  was  the  single  etiological 
entity  considered  in  connection  with  equine  piroplasmosis.  In 
1910,  however,  Nuttall  and  Strickland  (46)  reported  the  rosette 
or  cross-form  type  of  organism,  which  had  previously  been  con- 
sidered merely  a  form  of  Piroplasma  cabalh,  as  a  distinct  and 
separate  type  of  blood  parasite  and  termed  it  "Nuttalha  equi." 

At  present  the  findings  of  Nuttall  and  Strickland  are  generally 
accepted  and  two  types  of  organism  recognized.  However,  as 
mixed  infections  are  not  of  rare  occurrence,  and  as  it  has  been 
practically  impossible  to  differentiate  clinically  the  disease  induced 
by  these  two  types  of  organism,  no  attempt  has  been  made  to 
separate  the  two  affections.  Thus,  the  term  "equine  piroplas- 
mosis" includes  those  diseases  caused  by  either  one  or  both  of  the 
organisms  mentioned. 

Equine  piroplasmosis  is  of  frequent  occurrence  in  Russia,  Italy, 
Africa  and  India.  While  it  is  not  known  to  exist  in  the  continental 
United  States,  it  has  been  recognized  on  the  Canal  Zone. 

Horses  which  have  recovered  from  the  disease  may  harbor  the 
organism  in  their  blood  for  years  and  through  the  agency  of  ticks 
(the  natural  mode  of  infection)  infect  healthy  animals. 

Habitat  of  the  organism.  Carriers  of  Piroplasma  caballi  and 
Nuttallia  equi  harbor  the  parasites  in  some  of  their  red  blood 
corpuscles.  The  number  of  red  cells  which  may  be  found  to  con- 
tain the  organisms,  however,  is  exceedingly  small  as  compared  to 
that  in  actual  cases  of  the  disease. 

Detection  and  management.  Carriers  of  Piroplasma  caballi  and 
Nuttallia  equi  may  be  detected  through  microscopic  examination 
of  stained  blood-smear  preparations  from  such  animals.  It  is 
often  necessary,  however,  to  examine  a  large  number  of  prepara- 
tions at  different  periods  before  the  organism  can  be  demonstrated. 

Piroplasma  caballi  represents  the  true  type  of  Piroplasma  and 
resembles,  rather  closely,  Piroplasma  bigeminum,  the  causative 
agent  of  Texas  fever  in  cattle.  It  appears  as  a  relatively  large, 
elongated  or  pyriform  body,  averaging  approximately  3  to  3.5 
microns  in  length  and  is  usually  found  in  the  red  blood  cell  in 
pairs  or  singly. 


ORGANISMS   PATHOGENIC    FOR   LOWER   ANIMALS    ONLY        171 

Nuttallia  equi  is  considerably  smaller  than  Piroplasma  caballi 
and  is  characterized  by  its  occurrence  in  rosette  or  cross-forms, 
four  parasites  being  thus  grouped.  Occasionally  there  may  be 
observed  small  ring-like  or  coccus  forms  of  the  Nuttallia. 

At  present  there  is  no  known  medicinal  agent  which  has  given 
satisfactory  results  in  eliminating  these  organisms  from  the  blood 
stream.  Thus,  in  countries  or  locahties  where  equine  piroplas- 
mosis  has  not  become  established  the  detection  of  a  carrier  of  the 
infection  would  call  for  its  immediate  destruction.  In  communi- 
ties where  the  disease  is  prevalent,  however,  such  procedure  would 
not  be  feasible,  especially  when  it  is  considered  that  a  vast  number 
of  animals  in  such  places  are  carriers  of  the  organisms.  In  these 
localities  only  young  native  animals  become  affected,  the  older 
horses,  mules  and  donkeys  having  more  or  less  of  an  acquired 
immunity,  develop  the  disease  or  suffer  a  relapse  if  they  have 
previously  had  the  affection,  only  under  conditions  which  tend  to 
lower  their  normal  resistance. 

Susceptible  animals  should  be  kept  from  tick-infested  pastures, 
especially  during  the  warm  months  when  ticks  are  numerous. 
The  vaccination  of  susceptible  animals  according  to  the  method 
recommended  by  Theiler  demonstrated  that  passage  of  the  or- 
ganism through  donkey  colts  reduces  the  virulence  of  the  para- 
site, especially  for  horses  who  are  more  susceptible  to  the  disease 
than  mules  and  donkeys.  In  carrying  out  the  vaccination  of 
susceptible  animals,  blood  containing  parasites  which  have  been 
passed  through  4  or  more  donkey  colts,  is  used  as  the  inoculum. 
Susceptible  animals  are  injected  with  1  cc.  of  such  blood.  Such 
inoculation  gives  rise  to  but  a  minor  reaction.  Pregnant  mares 
and  animals  in  poor  condition  should  not  be  vaccinated.  As  in 
bovine  piroplasmosis,  vaccination  actually  produces  a  large  num- 
ber of  carriers. 

C.    CARRIERS   OF   FILTERABLE   VIRUSES 

1 .  The  virus  of  equine  infectious  anemia 

Equine  infectious  anemia,  manifesting  itseK  as  an  acute  or 
chronic,  septicemic  affection  with  marked  destruction  of  red  blood 
corpuscles,  is  one  of  those  diseases  of  horses  caused  by  an  ultra- 


172  CARRIERS   IN   INFECTIOUS   DISEASES 

microscopic  filterable  virus,  in  which  carriers  are  recognized. 
The  malady  is  prevalent  in  several  of  the  European  countries,  in 
Canada,  and  in  the  United  States  has  been  recognized  in  Minne- 
sota, South  Dakota,  Nebraska,  Nevada,  Kansas,  New  York, 
Virginia  and  Texas.  It  is  undoubtedly  more  widespread  than  is 
generally  believed. 

In  practically  all  instances  the  disease  eventually  has  a  fatal 
termination.  Animals  which  have  the  chronic  form  of  the  affec- 
tion sometimes  make  an  apparent  recovery,  continuing  in  health 
for  months  or  even  years.  Almost  without  exception,  however, 
they  suffer  relapses  which  finally  terminate  fatally.  Such  ap- 
parently recovered  horses  are  "relapsing  carriers,"  They  con- 
tinue to  harbor  the  virus  in  their  bodies  and  through  its  elimina- 
tion in  the  urine,  are  a  menace  to  the  health  of  other  animals. 

Habitat  of  the  virus.  The  virus  of  equine  infectious  anemia  is 
present  in  the  blood  stream  of  carriers  and  is  ehminated  more  or 
less  continuously  in  the  urine. 

The  blood  findings  in  infectious  anemia  vary  with  improvement 
of  the  animal,  so  that  usually  in  carriers  which  have  apparently 
recovered,  the  shortage  of  red  corpuscles  is  very  moderate  as 
compared  with  the  marked  diminution  (10  to  25  or  even  50  per 
cent)  of  blood  cells  in  active  cases. 

Detection  and  majiagement.  Positive  identification  of  carriers 
of  the  virus  of  infectious  anemia  can  only  be  made  through  the 
inoculation  of  normal  horses  with  blood  specimens  from  sus- 
pected carriers.  In  positive  cases  a  test  horse  given  an  intra- 
venous inoculation  of  25  to  50  cc.  of  blood  or  blood  serum  (the 
particular  amount  apparently  has  no  effect  on  the  incubation 
period)  usually  develops  the  disease  within  eight  or  nine  days, 
although  in  rare  instances  two  or  three  weeks  may  elapse  before 
the  development  of  symptoms.  In  some  cases  such  test  animals 
may  die  within  two  or  three  weeks  after  the  development  of 
symptoms.  Again  they  may  develop  the  chronic  type  of  the 
disease  in  the  very  beginning.  Such  cases  run  a  rather  long 
course  before  developing  more  manifest  symptoms  of  the  disease 
than  periodical  rises  in  temperature. 

When  obtainable,  a  definite  history  of  a  previous  attack  of 
infectious  anemia  in  a  suspected  carrier,  is,  for  practical  purposes, 
sufficient  to  incriminate  the  animal. 


ORGANISMS   PATHOGENIC    FOR   LOWER   ANIMALS   ONLY       173 

In  view  of  the  fact  that  carriers  of  the  virus  of  infectious  anemia, 
besides  menacing  the  health  of  other  horses,  abnost  invariably 
suffer  relapses  which  finally  terminate  fatally,  they  should  be 
promptly  destroyed  and  the  carcasses  properly  disposed  of. 

2.  The  virus  of  contagious  pleuro-pneumonia  of  cattle 
("Asterococcus  mycoides") 

Contagious  pleuro-pneumonia  of  cattle  is  an  acute,  subacute, 
and  occasionally  chronic,  disease  of  cattle,  characterized  by  exu- 
dative inflammation  of  the  interlobular  lymph  vessels  and  alveolar 
tissue  of  the  lungs,  with  a  sero-fibrinous  pleurisy. 

The  disease  at  present  does  not  exist  in  the  United  States,  the 
last  case  in  this  country  being  destroyed  in  1892.  This  scourge, 
however,  has  made  its  appearance  in  the  United  States  several 
times  and  has  been  eradicated  only  through  energetic  efforts  of 
the  federal  Department  of  Agriculture  in  cooperation  with  the 
authorities  in  the  states  involved.  During  1886,  in  the  state  of 
Illinois  alone,  approximately  10,000  cattle  were  affected  with  the 
disease. 

Contagious  pleuro-pneumonia  is  caused  by  a  very  minute  virus 
which  will  pass  the  Berkefeld  filter  and  the  Chamberland  cylinder 
of  "F"  porosity,  but  is  held  back  by  the  Chamberland  "B"  filter. 
It  is  possible  to  cultivate  the  organism  artificially  in  Martin's 
bouillon  containing  beef  serum,  and  also  in  several  other  types  of 
serum  media.  When  magnified  approximately  1500  diameters 
with  considerable  illumination,  the  organisms  are  seen  as  poly- 
morphic bodies,  appearing  as  minute  refracting  dots,  very  short 
spirillae,  and  branching  and  asteroid  figures.  Borrel  (47)  and 
his  associates  in  studying  the  pleomorphic  nature  of  the  organism 
observed  coccic,  streptococcic  and  morula-shaped  forms,  as  well 
as  short,  spiral  threads,  showing  fork-shaped  branchings,  and 
asteroid  and  mycelioid  bodies,  surrounded  with  a  fine  mucin  cover- 
ing. Because  of  these  findings  he  termed  the  organism  "Astero- 
coccus  mycoides." 

Animals  which  have  apparently  recovered  from  contagious 
pleuro-pneumonia  have  been  known  to  harbor  and  transmit  the 
virus  to  healthy  animals  several  months  to  two  or  three  years 
subsequently.  The  great  percentage  of  such  recoveries,  however, 
are  more  apparent  than  real  as  relapses  in  arrested  cases  usually 


174  CARRIERS   IN   INFECTIOUS   DISEASES 

occur.  The  majority  of  these  carriers,  therefore,  come  in  the 
category  of  "relapsing  carriers." 

Habitat  of  the  virus.  The  virus  of  contagious  pleuro-pneumonia 
is  usually  found  in  sequestrated  and  encapsulated  lesions  in  the 
lungs  of  animals  which  harbor  the  infection  following  apparent 
recovery. 

Autopsy  of  such  animals  reveals  in  one  or  both  lungs,  a  single, 
rarely  several,  so-called  "sequesters."  In  these  lesions  areas  of 
the  lobular  tissue  have  undergone  necrosis.  The  necrotic  portion 
is  surrounded  by  a  dense  connective  tissue  capsule,  the  necrotic 
piece  lying  free  (occasionally  partty  adherent)  in  the  cavity  thus 
formed.  This  necrotic  piece,  in  cases  which  are  not  of  too  long 
standing,  consists  of  a  soft,  mushy,  outer  portion  and  a  rather 
firm  inner  part,  which  on  section  appears  mottled.  In  long- 
standing cases  this  tissue  breaks  down,  forming  a  thick,  greasy, 
pasty  mass.  When  such  lesions  are  comparatively  small  they  may 
gradually  become  absorbed.  In  a  large  percentage  of  cases, 
however,  the  process  subsequently  breaks  through  the  limiting 
capsule,  giving  rise  to  a  recurrence  of  the  acute  condition,  with 
spread  of  the  infection.  When  these  "sequesters"  are  entirely 
closed  by  the  connective  tissue  capsule  the  virus  in  the  lesion  is 
held  in  such  locality.  However,  when  they  communicate  with 
a  bronchus  infectious  material  is  more  or  less  continuously 
expelled. 

The  circulating  blood  is  not  favorable  for  the  propagation  of 
the  virus  of  contagious  pleuro-pneumonia,  hence,  in  carriers,  it  is 
not  harbored  in  the  blood  stream. 

Detection  and  management.  Detection  of  carriers  of  the  virus  of 
contagious  pleuro-pneumonia  is  practically  impossible  of  accom- 
phshment  through  examination  of  the  suspected  animal  in  the 
living  state.  History  of  cases  of  the  disease  associated  with  cer- 
tain animals,  and  knowledge  of  previous  puhnonary  affections  in 
suspected  carriers,  constitute  incriminating  evidence. 

As  no  satisfactory  treatment  is  known  for  contagious  pleuro- 
pneumonia, and  as  apparently  recovered  animals  carrying  the 
virus  are  prone  to  suffer  relapses,  cattle  shown,  with  a  reasonable 
degree  of  certainty,  to  harbor  the  infection  should  be  slaughtered. 
Definite  history  of  a  previous  attack  of  the  disease  in  a  suspected 
carrier  is  ample  evidence  for  its  destruction. 


ORGANISMS   PATHOGENIC   FOR   LOWER   ANIMALS   ONLY       175 

3.  The  virus  of  equine  influenza 

Influenza,  "pink  eye"  or  "shipping  fever,"  is  a  common  and 
important  disease  of  the  equine  species.  It  manifests  itself  as  an 
acute,  febrile  contagion,  characterized  by  a  catarrhal  inflammation 
of  the  mucous  membranes,  especially  those  of  the  head  region. 
Further,  inflammatory  or  edematous  swellings  in  various  parts  of 
the  subcutis  and  the  tendons  are  common  to  the  affection. 

The  etiology  of  the  disease  has  been  more  or  less  obscure  but 
in  view  of  positive  transmission  experiments  conducted  by  a 
number  of  investigators  with  filtered  inoculums,  it  is  generally 
accepted  that  the  causative  agent  is  a  filterable  virus. 

Stallions  which  have  recovered  from  the  disease  may  harbor  the 
virus  in  their  bodies  and  infect  healthy  mares  through  coitus 
several  months  or  even  one  or  two  years  following  recovery  from 
the  disease.  Poels  (48)  was  able  to  infect  healthy  horses  through 
intravenous  injections  of  filtered  semen  from  a  stallion  which  for 
a  number  of  months  had  infected  mares  bred  to  it.  Basset  (49) 
demonstrated  the  blood  of  a  horse  which  had  recovered  from  an 
artificial  inoculation,  to  be  infectious  for  three  and  one-half 
months  subsequently. 

Habitat  of  the  virus.  Nothing  is  known  regarding  the  habitat 
of  the  influenza  virus  in  the  body  of  carriers  aside  from  the  fact 
that,  occasionally,  it  may  be  demonstrated  in  the  blood  and  in 
stallions  in  the  semen.  Because  of  its  presence  in  the  blood  it  is 
undoubtedly  eluninated  periodically  in  the  urine. 

Detection  and  management.  A  stallion  may  readily  be  suspected 
of  being  a  carrier  of  the  influenza  virus  when  there  is  frequent 
history  of  influenza  in  various  mares  which  he  serves.  According 
to  Hutyra  and  Marek  (50)  the  disease  invariably  develops  in  from 
six  to  nine  days  where  infection  is  brought  about  through  coitus. 
The  identification  of  a  carrier  of  the  influenza  virus,  however,  is 
only  estabUshed  by  the  transmission  of  the  disease  to  a  normal 
animal  through  the  inoculation  of  blood,  semen,  or  other  specimens 
from  the  suspected  animal. 

Animals  known  to  harbor  the  influenza  virus  should  not  be 
permitted  to  come  in  contact  with  susceptible  animals.  Stallions 
shown  to  be  carriers  should  not  be  permitted  to  serve  mares. 


176  CARRIERS   IN   INFECTIOUS   DISEASES 

Apparently  no  attention  has  been  paid  to  the  treatment  of 
carriers,  hence,  there  is  no  data  available  on  the  value  of  various 
drugs  which  might  be  employed  with  a  view  to  eliminating  the 
virus  harbored  by  such  animals.  In  Germany  salvarsan  and  neo- 
salvarsan  have  been  extensively  used  in  the  treatment  of  equine 
influenza  and  its  complications  with  apparently  good  results  in  a 
certain  percentage  of  cases.  In  carriers  of  the  influenza  virus, 
especially  valuable  stallions,  the  use  of  salvarsan  or  other  arsenical 
products  may  be  of  value  in  destroying  the  infection. 

4.  The  virus  of  hog  cholera 

Occasional  reference  is  made  in  the  Hterature  on  hog  cholera, 
to  possible  carriers  of  the  filterable  virus  of  the  disease  among 
apparently  recovered  hogs.  Further,  the  so-called  "runts"  which 
have  had  a  chronic  type  of  the  affection  have  often  been  considered 
carriers  of  the  infection.  There  appears,  however,  to  be  no  rec- 
ords of  carrier  investigations  in  hog  cholera,  definitely  establishing 
the  existence  of  true  carriers  of  the  virus. 

Dorset  (51)  and  his  associates  in  experiments  to  determine 
whether  or  not  several  recovered  hogs  harbored  the  cholera  virus, 
carried  out  exposure  and  inoculation  tests  with  entirely  negative 
results. 

Hog  cholera  has  undoubtedly  been  transmitted  to  healthy 
animals  by  "runts."  From  present  information,  however,  it 
appears  that  when  such  animals  are  capable  of  disseminating  the 
infection  they  are  more  Hkely  to  be  actually  suffering  from  the 
chronic  form  of  the  disease  than  harboring  the  virus  as  carriers. 

While  it  is  entirely  possible  that  there  are  instances  of  real 
carriers  of  the  hog  cholera  virus,  at  present  we  are  without  infor- 
mation on  the  subject. 


CHAPTER  XX 
Conclusion 

There  exist  among  animals  carriers  of  organisms  of  infectious 
diseases  just  as  they  are  found  among  members  of  the  human 
family.  The  problem  in  veterinary  medicine,  however,  differs 
in  many  respects  from  that  in  human  medicine. 

As  in  the  case  of  man,  carriers  among  animals  disseminate  in- 
fection through  their  respiratory,  intestinal  and  genito-urinary 
tracts,  and  indirectly  through  insects,  but  in  addition  we  have 
milch  animals  harboring  and  eliminating  organisms  from  their 
udders.  Further,  with  food-producing  animals  the  carrier  problem 
does  not  always  end  with  the  death  of  the  animal.  Harbored 
organisms  may  be  transmitted  to  man  through  meat  or  meat-food 
products. 

Under  natural  conditions  animals  are  obviously  more  intimately 
associated  than  human  individuals,  affording  conditions  under 
which  the  carrier  functions  most  effectively.  Then  the  scavenging 
propensities  of  various  species  promote  the  carrier  problem. 
Hogs,  various  wild  animals  and  buzzards,  for  example,  are  con- 
tinually ingesting  a  vast  variety  of  organisms,  a  number  of  which 
may  persist  in  the  intestinal  tracts  of  such  animals  for  variable 
periods  of  time,  thus  serving  as  a  source  of  infection  for  susceptible 
species. 

The  large  number  of  species  of  animals  with  marked  variation 
in  susceptibility  to  certain  infectious  diseases,  often  permits 
members  of  one  species  to  serve  as  reservoirs  of  infection  for  ani- 
mals of  a  more  susceptible  species.  This  is  well  illustrated  in 
trypanosomiasis. 

In  carrier  work  in  veterinary  medicine  an  outstanding  feature 
is  the  fact  that  serological  tests  can,  in  a  number  of  instances,  be 
employed  to  good  advantage.  While  such  tests  may  not  differ- 
entiate the  carrier  from  the  case,  and  may  miss  some  carriers, 
nevertheless  in  numerous  cases  these  tests  will  narrow  the  problem 

177 


178  CARRIERS   IN    INFECTIOUS   DISEASES 

by  identifying  animals  which  are  then,  or  have  previously  been, 
infected  with  a  particular  type  of  organism. 

A  notable  feature  of  the  carrier  problem  in  veterinary  medicine 
is  the  vast  number  of  carriers  in  certain  of  the  infectious  diseases. 
In  bovine  piroplasmosis,  for  example,  the  great  percentage  of 
cattle  in  infected  districts  are,  or  have  been,  carriers. 

In  the  control  of  carriers  among  veterinary  subjects  ability  to 
slaughter  animals  harboring  pathogenic  organisms,  where  such 
procedure  is  feasible,  is  a  distinct  advantage.  In  addition,  control 
is  more  perfect  because  the  personal  element  is  largely  eliminated. 

LITERATURE  CITED 

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(2)  MoHLER  AND  Hart:  Annual  Report,  Chief,  U.  S.  Bureau  of  Animal 

Industry,  1908. 

(3)  Saisawa:  Zeitschrift  fiir  Hygiene  und  Infektionskrankheiten,  Leipzig, 

1912,  Ixx,  177. 

(4)  Evans,  Alice  C.  :  Jour.  Infectious  Diseases,  1918,  xxii,  580. 

(5)  Annual  Report,  Chief,  U.  S.  Bureau  of  Animal  Industry,  1921. 

(6)  MoHLER   AND   BucKLEY :  Annual  Report,   Chief,   U.   S.    Bureau  of 

Animal  Industry,  1902. 

(7)  O'Brien:  X.  P.,  231  (1910). 

(8)  Heuser:  Zeitschrift  fiir  Hygiene  und  Infektionskrankheiten,  Leipzig, 

1910,  Ixv,  8. 

(9)  ZwicK  AND  Weichel:  Ibid.,  xxxviii,  1911,  327. 

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(45)  Schroeder  and  Cotton:  Personal  communication. 

(46)  NuTTALL   AND   STRICKLAND :  Centralblatt   fur   Bakteriologie.    Para- 

sitenkunde  und  Infektionskrankheiten,  1910,  Ivi,  524. 

(47)  BoRREL  Dxjjardin-Beatjmetz,  Jeantet  and  Jouan:  Ibid.,  168. 

(48)  PoELs:  Cited   from    Special  Pathology    and    Therapeutics    of    the 

Diseases  of  Domestic    Animals.     Hutyra    and  Marek,  English 
trans.,  vol.  1,  pp.  183,  1916. 

(49)  Basset:  Comptes  rendus  des  seances  de  I'Academic   des  Sciences 

(Paris),  1911,  cliii,  485. 

(50)  Hutyra  and  Marek  :  Special  Pathology  of  the  Diseases  of  the  Domes- 

tic Animals.     English  trans.,  vol.  1,  pp.  185,  1916. 

(51)  Dorset,   McBride,    Niles   and   Rietz:  Investigations   Concerning 

the  Sources  and  Channels  of  Infection  in  Hog  Cholera.     Jour. 
Agric,  Research,  xiii,  no.  2,  April  S,  1918. 


INDEX 


Abortion,   bovine,    infectious,    car- 
riers among  cattle,  153 
Alimentary  diseases,  43 
Amoebiasis,  human,  66 
carriers  among  fowls,  160 
carriers  among  monkeys,  160 
Anthrax,  carriers  among  hogs,  135 
Anemia,     infectious,     equine,     car- 
riers of  virus  among  horses,  171 
Aphthous    fever,     carriers    among 

cattle,  147 
Applicants,  examination  of,  115 
Asterococcus  mycoides,  173 
see      pleuro-pneumonia,      conta- 
gious, cattle,  173 


B 


Bacterium  abortus  (Bang),  carriers 
among  cattle,  153 

Bacillus  aerogenes  capsulatus, 
carriers  among  animals,  143,  144 

Bacillus  aertrycke,  carriers  among 
animals,  129 

Bacillus  anthracis,  carriers  among 
hogs,  135 

Bacillus  bipolaris  septicus,  carriers 
among  animals,  161 

Bacillus  botulinus,  carriers  among 
animals,  143,  144 

Bacillus  coli,  carriers  among  ani- 
mals, 143,  144 

Bacillus  diphtheriae,  carriers  among 
animals,  137 

Bacillus  enteritidis  (Gaertner),  car- 
riers among  animals,  129 

Bacillus  erysipelatis  suis,  carriers 
among  hogs,  141 


Bacillus   lactis  aerogenes,    carriers 

among  animals,  144 
Bacillus    mallei,     carriers     among 

horses,  136 
Bacillus       necrophorus,       carriers 

among  animals,  162 
Bacillus    oedematis    maligni,    car- 
riers among  animals,  134 
Bacillus  paratuberculosis,    carriers 

among  cattle,  164 
Bacillus  paratyphosus,  45 

carriers  among  animals,  129 
Bacillus  pestis,  carriers  among  rats 

and  squirrels,  139 
Bacillus  phegmasis  uberis,  carriers 

among  animals,  144 
Bacillus  prqteus  mirabilis,  carriers 

among  animals,  144 
Bacillus       pyocyaneus,        carriers 

among  animals,  143,  144 
Bacillus  pyogenes,  carriers  among 

animals,  143,  144 
Bacillus  suipestifer,  carriers  among 

animals,  129 
Bacillus     tetani,     carriers     among 

animals,  132 
Bacillus  tuberculosis,  99,  125 
carriers  among  cattle,  126 
carriers  among  hogs,  127 
Bacteria,    animal   carriers   of   bac- 
terium pullorum,  6,  123,  151,  161 
carriers  among  fowls,  166 
Bacterium        tularense,        carriers 

among  squirrels  and  rabbits,  140 
Balantidium   eoli,    carriers    among 

hogs,  160 
Balantidiosis,  human,  69 
Blood  group  of  diseases,  44 


181 


182 


INDEX 


Cats,  carriers  of  B.  diphtheriae,  137 
carriers    of    miscellaneous    bac- 
teria, 143 
Cattle,     carriers    of    B.    bipolaris 
septicus,  160 
carriers    of     B.    oedematis    ma- 

ligni,  134 
carriers      of    B.     paratuberculo- 

sis,  164 
carriers  of  B.  tetani,  132 
carriers  of  B.  tuberculosis,  126 
carriers  of  Bact.  abortus  (Bang), 

153 
carriers    of    miscellaneous    bac- 
teria, 143 
carriers    of    organisms    of    Sal- 
monella group, 129 
carriers  of  piroplasmata,  167 
carriers  of  streptococcus  of  bovine 

mastitis,  151 
carriers    of   virus    of    contagious 

pleuro-pneumonia,    173 
carriers    of    virus    of    foot-and- 
mouth  disease,  147 
Cholecystitis,  29,  48,  56,  131 
Cholera,  60 

Cholera,  hog  carriers,  176 
Classification,  15 

Coccidia,      carriers      among      ani- 
mals, 160 


Dermatitis,  gangrenous,  equine,  162 
Diarrhea,  white,  of  fowls,  166 
Diphtheria,  72 

carriers  among  animals,  137 
Dogs,      carriers      of      Leishmania 
canis,  145 

carriers    of    miscellaneous    bac- 
teria, 143 
Dourine,  animal  carriers,  158 
Duodenal  contents,  51 
Dysentery,  amoebic,  66 

bacillary,  64 


Enteriditis   group  of  organisms,  see 

Salmonella  group  129 
Enteritis,  paratuberculous,  bovine, 

164 

bovine,  164 
Erysipelas,  swine,  141 


Filariasis,  103 
Filterable  viruses,  100 

animal  carriers  of,  147,  171 
Food  handlers,  115 
Foot-and-mouth  disease,  115 

carriers  among  cattle,  147 
Foot-rot  of  sheep,  162 
Fowls,  carriers  of  amoebae,  160 

carriers     of     B.     bipolaris     sep- 
ticus, 161 

carriers  of  B.  pullorum,  166 


Gaertner    group,     see    Salmonella 

group, 129 
Glanders,  carriers  among  horses,  136 
Goats,  carriers  of  M.  melitensis,  123 
Gonorrhoea,  106 

Guinea      pigs,      carriers      of      B. 
aertrycke,  129 
carriers  of  B.  suipestifer,  129 
carriers  of  B.  tetani,  132 

H 

Helminthoses,  70 

Hemorrhagic      septicemia      group, 
animal  carriers,  161 

Hogs,  carriers  of  B.  anthracis,  135 
carries  of  B.  bipolaris  septicus  161 
carriers  of  B.  botulinus,  144 
carriers  of  B.  erysipelatis  suis,  141 
carriers  of  B.  necrophorus,  162 
carriers     of     B.    oedematis    ma- 

ligni,  134 
carriers  of  B.  tetani,  132 
carriers  of  B.  tuberculosis,  127 


183 


Hogs, — Continued. 

carriers  of  Balantidium  coli,  160 
carriers    of    miscellaneous    bac- 
teria, 143 
carriers    of    organisms    of    Sal- 
monella group, 129 
Hookworm  disease,  70 
Horses,    carriers    of    B.    bipolaris 
septicus,  161 
carriers  of  B.  mallei,  136 
carriers     of     B,     edematis     ma- 

ligni,  134 
carriers  of  B.  tetani,  132 
carriers     of    miscellaneous    bac- 
teria, 143 
carriers  of  Nuttallia  equi,  170 
carriers  of  piroplasma,  170 
carriers   of   virus   of   equine   in- 
fluenza, 175 
carriers     of    virus    of    infectious 
anemia,  171 
Hygiene,  112 

I 

Influenza  bacillus,  97 
Influenza,  equine  carriers  of  virus 
among  horses,  175 


Johne's  Disease  in  cattle,  carriers 
of,  164 

K 
Kala-azar  in  dogs,  carriers,  145 

L 

Laboratory  work,  34 

Leishmania  canis,  carriers  among 
dogs,  145 

Leishmaniasis,  canine,  see  Leish- 
mania canis,  145 

Lip-and-leg  ulceration  of  sheep,  162 

M 

Malaria,  101 

Mai  de  caderas  of  horses,  157 


Malta    fever  in  goats,  see  M.  meli- 

tensis,  123 
Mastitis,    bovine,     infectious,    see 

Strep,  of  bovine  mastitis,  151 
Meningitis,  79 
Mice,     carriers     of     organisms     of 

Salmonella  group,  130 
Military  services,  116 
Miscellaneous  bacteria  carried  by 

animals,  143 
Monographs,  5 

N 

Nagana  in  animals,  157 
Nuttallia  equi,  170 


Paratyphoid  group,  see  Salmonella 

group, 129 
Phorology,  14 

Physical  examinations,  116 
Piroplasma  caballi,  carriers  among 

horses,  170 
Piroplasmata  bigeminum  and  bovis, 

carriers  among  cattle,  167 
Piroplasmosis  of  cattle,  167 
Piroplasmosis  of  horses,  170 
Plague,    bubonic,    carriers    among 

rats  and  squirrels,  139 
Pneumonia,  87 
Preventive  medicine.  111 
Protozoa,    animal   carriers   of   145, 

156, 159,  167 
Pyelitis,  33,  49 


Rabbits,  carriers  of  B.  tetani,  133 
carriers  of  Bact.  tularense,  141 

Rats,  carriers  organisms  of  Salmon- 
ella group, 130 
carriers,  of  B.  pestis,  139 

Records,  118 

Recruits,  117 

Red-water,  British,  of  cattle,  167 

Respiratory  diseases,  44 


184 


INDEX 


Rodents,     carriers     organisms     of 

Salmonella  group,  130 
Rules  of  hygiene,  113 

S 

Salmonella  group  of  organisms,  129 

carriers  among  animals,  129 
Sanitation,  111 
Sexual  diseases,  44,  114 
Sheep,    carriers    of    B.    oedematis 
maligni,  134 
carriers  of  B.  tetani,  132 
carriers    of    miscellaneous    bac- 
teria, 143 
Specimens  of  feces,  51 
Specimens  from  nasopharynx,  82 
Squirrels,  carriers  of  B.  pestis,  139 

carriers  of  Bact.  tularense,  140 
Staphylococci,  carriers    among  ani- 
mals,   143 
Streptococcus,  of  bovine  infectious 
mastitis,  151 
carriers  among  cattle,  151 


Streptococci,  90 

carriers  among  animals,  143 
Surra,  carriers  among  animals,  157 
Syphilis,  104 

T 

Tetanus,  animal  carriers,  132 
Texas  fever  of  cattle,  167 
Tonsillitis,  26,  74 
Trypanosoma,  Brucei,  157 

equinum,  157 

equiperdum,  157 

Evansi,  157 
Trypanosomiasis,    animal    carriers, 

156 
Tuberculosis,  99,  125 
Tularemia,  140 
Typhoid,  45 

V 

Vaccination,  113 

Veterinary  medicine,  carriers  in,  121 

conclusion  to  section  on,  177 
Vibrion     septique,      animal     car- 
riers, 134 
Vincent's  angina,  98 


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^^    «8  1932 
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NOV  30  193? 


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DEC   28  1937 


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